Plagg works with Adrien to help him become Cat Noir, but he doesn't show great amounts of dedication towards him most of the time. He once hid from Adrien instead of coming out to help him when Stormy Weather was on the loose, and the only thing that lured him out was Camembert. He often teases him, usually for his impossible love for Ladybug, or points out questionable decisions when he isn't opting for doing them himself. However, he refers to Ladybug as the love of Adrien's life and questions why he didn't take the chance to find out her secret identity after the battle with Lady Wifi.
However, Plagg has shown that he does care for Adrien, like when he asks if he's okay when his father doesn't appear for parent show-and-tell at school and in "Santa Claws" when he genuinely tells Adrien "Merry Christmas." Plagg once lets Adrien neglect his duties as Cat Noir, suggesting that he should have fun at his birthday party before trapping the Bubbler's akuma. He also gives him cheese, something he doesn't usually share, for his birthday, even though Adrien doesn't want it and Plagg eats it for him. Also, unlike Tikki, he doesn't pressure him when it comes to working. He is informative to Adrien at times, like when he warns him that they can't transform in "Rogercop" while Chloé's bracelet is stuck on Plagg's head, as it would damage Cat Noir's powers. In "Simon Says", Plagg looks concerned and sad for Adrien when Gabriel hugs him and leaves quickly when he notices Adrien's ring for the first time. Also as a sign that he cares, is in "Glaciator", believing that Adrien had a heartache, Plagg offers to share his cheese with him. Plagg also attempts to cheer Adrien up in "Captain Hardrock" by performing a brief concert for him when he wasn't allowed to go to his friends' concert.
He also tried to cheer Adrien up in "The Puppeteer 2" and also in "Feast", when Nathalie's condition made him think of his mother. By playing a duet with him on the piano causing Adrien laugh.
In "Syren", when Adrien threatened to remove his Miraculous if Plagg doesn't spill his secrets. He admits in a way that Adrien is his close friend. But when Master Wang Fu arrives Plagg is relieved that he doesn't have to hide secrets from Adrien. In "Sandboy", he can easily tell the real Adrien from a fake Adrien quoting, "The real one talks nonsense but it's never this bad." Seeing the damage, Plagg hoped he was okay and was relieved he survived his nightmare. After the ordeal he embraced Adrien for letting him have his freedom (mostly) and being the best Cat Noir ever.
In "Style Queen", he shows great concern for Adrien when he is turned into a golden statue by the villain. In "Frozer", Plagg jokes on how he greets a Camembert before eating it as an advice for Adrien who is unsure about whether Ladybug is his only crush after giving a rose to Kagami Tsurugi, though Adrien thinks that Plagg should give this piece of advice to someone else.
In "Mayura", Plagg rarely but also generously shared his Camembert with Adrien, which the latter, unlike how he normally would instinctively detest it, gladly accepted.
In "Chameleon", after Lila's akumatized villain form kissed Adrien on the lips, he fell into an enchanted sleep and was shoved into a locker. Plagg tried to wake him up to no avail and wondered what to do then, he tried to give him an enchanted kiss to wake him up. When Adrien woke up, he asked Plagg what was he doing and said nothing and explained what happened with Lila he advised Adrien to be more careful picking his friends.
During "Stormy Weather 2", when Adrien believes that his life hasn't change nor will his father Plagg thought otherwise reminding him of everything that happen since last summer vouching that his life had changed for the better.
During "Oblivio", since Plagg lost his memory he couldn't remember what or who Adrien was and refused to help him against the villain. He gets so tire of the situation that he leaves, but as Plagg goes begins to see billboards of Adrien everywhere at first calling psychological harassment. But upon seeing Oblivio's bubble and remembering Tikki's words, he returns to Adrien asking if he can help.
Aware of Lila's deceitful nature in "Oni-Chan", Plagg asked Adrien why is he being nice to her warning him of how sneaky she is.
He is also aware of Adrien's status as a model and that he has many lady fans seen in "Dark Cupid". But when he sees the photo that Lila posted caused Kagami's akumatization in "Oni-Chan", Plagg calls her another admirer knowing that with so many lady fans hovering around Adrien that they would end up fighting over him. The kwami refers to them again in "Stormy Weather 2", when Plagg questioned Adrien's love for Ladybug again grabbing a pile Valentine Day cards he suggested picking another girl who's available.
In "Reflekdoll", when getting ready for Marinette's photoshoot Plagg advised Adrien not to remove his ring but was in charge of guarding it but seeing Reflekta and her sentimoster's destruction he found the ring and went looking for Adrien but found Marinette instead. After the titular villain's defeat, Plagg was happily reunited with him, and happy that he won't remove the ring again.
Plagg tried to warn Adrien about using another Miraculous especially since he couldn't be two different heroes at the same time. But seeing that he was so love struck that Ladybug picked him to wield the Snake Miraculous in "Desperada", he gave up trying to reason with him. As Aspik, he scolded Adrien for not listening to him, but after the final time he was happy that Adrien came to his senses and encouraged him to make up the experience as Cat Noir.
He received a scolding from Adrien about wondering off and being spotted by another person in "Kwamibuster". Plagg also mentions Tikki to Adrien leading him to figuring out the heroine's identity which left him worried. He warned him if his or Ladybug's identity gets out then they can't be their alter egos giving up their jewels. Upon being set free Plagg reunited with Adrien giving him advice about coming up with a story to hide his identity.
In "Sandboy", after leaving Adrien; he meets with Tikki on a rooftop affectionately calls her "Sugarcube". And yet, they both share the concern of contacting Nooroo. Before leaving Master Fu's shop again he saw that Tikki was really close and affectionate with her owner Marinette.
During "Oblivio", when Plagg loses his memory he refuses to help a couple of "strangers" despite being convinced by Tikki. Having enough when she calls him selfish and a total coward, Plagg was offended and calls himself a free spirit.
He spends brief time with Tikki in "Reflekdoll", until the two were sent flying along with the limo seeing the sentimoster's destruction, Plagg helped remind her of the task at hand and assured her that everything would be okay. When comes to anything involving cheese he doesn't always listen to Tikki is in "Kwamibuster". Upon seeing the Science teacher Plagg is told why he should listen to her. Afterwards, when Tikki opted wanting to tell their owners or at least Master Fu Plagg calmed her nerves but when it resulted in the two getting captured. He tried to get out and offered to use his Cataclsym but was halted by Tikki saying he couldn't control his powers. Plagg thought Tikki might have a plan but was saddened that she didn't and expressed hoped that her owner would.
In "Stoneheart", he teases Adrien by referring to him and Marinette as "two lovebirds". In "Dark Cupid", unaware that the Valentine's Day card came from Marinette, upon reading it Plagg comments "that anyone who writes as sickeningly sweet as you must be your soulmate." While watching Fill My Shoes in "Troublemaker", Plagg sees all the pictures of Adrien in Marinette's room, calling her another secret admirer.
In "Style Queen", Plagg officially meets Marinette and tells her of his owner's recklessness. During "Sandboy", he can see that Marinette is really close and affectionate with Tikki.
In "Weredad", Plagg liked the idea of Marinette being Adrien's girlfriend especially when she is the daughter of the best baker in Paris, quietly commenting that Marinette and Ladybug are one and the same.
In "Stormy Weather 2", when questioning Adrien's love for Ladybug again he suggested that Adrien should pick another girl. Upon examining the letter and Marinette's note, Plagg ponders the possibility of the letter being from Marinette.
While looking for Adrien, upon someone seeing him Plagg thought he found his owner but upon hearing her voice he's surprised to meet Marinette again who was transformed into Reflekta in "Reflekdoll". Then, was asked a series of questions to which he tells her it's "a long story" and helps transform her into Lady Noir. After Reflekta's defeat, he recharges the two say their goodbyes agreeing that the time they had was awesome.
With Ladybug, Plagg knows that Adrien has a crush on her and how much she means to him, but he is skeptical about Adrien's feelings, reminding him that he doesn't know who Ladybug really is underneath the mask. However, he occasionally shows that he does get behind Ladybug and Adrien becoming a couple, like being upset with Adrien not staying around to see Ladybug detransform in "Lady Wifi". In "Riposte", Plagg respects Ladybug enough that he questions if Adrien should leave the place she hid him to transform. While not caring about it beforehand, he learns her secret identity in "Dark Owl", when he finds her plan to trick Dark Owl, involving detransforming, surprising.
In "Style Queen", Plagg saves Ladybug just as she was under the villain's mercy by performing Cataclysm onto the Eiffel Tower, buying Ladybug time to defeat her. She also sees the destructive power of his Cataclysm as it breaks the Eiffel Tower and replies saying "No wonder he wasn't allowed out". When she asked about Cat Noir's safety, Plagg assured her he'd watch over him.
Aware of the rules Plagg was worried when he spilled information to Adrien risking Ladybug's identity. He was also aware that Ladybug might have a plan however upon seeing more of his kwami brothers and sisters get captured, Plagg believed that Tikki's owner had failed in "Kwamibuster". But was surprised to see her instantly recognizing her despite having a different Miraculous and was set free.
Plagg and Gabriel have never met, and when Adrien suggests that his father is playing a prank on him with Plagg in "Stoneheart", Plagg adamantly warns Adrien that he can never reveal his secret identity to his father or anyone else. Although rarely commenting on it, Plagg can tell that a lot of Gabriel's actions toward Adrien make him very disappointed. The discovery of Gabriel's secret safe excites Plagg in "Volpina", though he quickly loses interest after seeing nothing interesting, other than thinking he may remember the book from somewhere.
In "The Collector", Plagg voiced concerns about Gabriel being able to see him thus revealing Adrien's identity as Cat Noir but was happy that kwamis couldn't be filmed or photographed. Like Adrien, Plagg is unaware that Gabriel is Hawk Moth, but in "Sandboy", he shudders at the idea of being discovered by him.
During "Stormy Weather 2", when Adrien expresses doubt over the possibility of his father changing, Plagg reminds Adrien of all the nice things his father has done for him and compares him to grind cheese, stating that its got a hard rind but soft inside.
Never having met Nino, Plagg knows that Adrien views him as his best friend. He reassures Adrien that they can save Nino from his akumatization after enjoying the party for a while in "The Bubbler", and he is very amused by Nino's attempt to reveal his feelings for Marinette in "Animan", listening to the conversation on Adrien's head.
Although never meeting her, Plagg doesn't care much for her. He has fun teasing Adrien about him possibly being in love her Chloé when they learn about Alya's belief in Chloé being Ladybug in "Lady Wifi". He also invades Chloé's bag for what looks like a box of Camembert, and after learning it isn't, he plays with her bracelet before it gets stuck on his head, leading to a lot of problems, including getting Marinette in trouble.
He is completely aware that Adrien doesn't have a crush on Chloé especially when he sees a nightmare version of him talking about being in love with her calling it nonsense in "Sandboy".
Similar to Tikki, Plagg is loyal to Wang Fu where he refused to tell Adrien any secrets in "Syren". But when Wang meets Adrien in person, Plagg happily introduces him. In spite of Master Fu being his guardian, as seen in "Style Queen", he disagrees with Master Fu's fact on how dangerous he can be and doesn't listen to the latter, which implies that Plagg won't fully obey anyone including Master Fu other than Adrien.Style Queen". And yet the two work well together when they tried to get in contact with Nooroo during his birthday in "Sandboy".
He hasn't met Lila in person but Plagg is aware of her since "Volpina" knowing that Adrien as himself wasn't enough to stop her.
In "Chameleon", he doesn't see her as good friend for Adrien after she puts him to sleep with an enchanted kiss. In "Oni-Chan", he is suspicious of Lila when she goes sneaking around Adrien's room aware that she lies frequently and was unsure what she was looking for.