Taking up a new hobby is fun and can be educational, but in TV Land, it's a risky business: it might just lead you to end up wanting to do it to the exclusion of other good/important things and have to either learn about moderation or give it up completely (if the latter applies, it may lead to Do Not Do This Cool Thing), and that's what this is.
The problem might lie in the fact that the character is isolating themselves from their friends or maybe they're getting unfit due to lack of exercise if it involves sitting down. Maybe they're forgetting basic things like food or sleep or are neglecting things like their job or their family, or the hobby gets in someone else's way. Or maybe they're spending so much money on expensive hobby gear that they're squandering their entire life savings. Sometimes there's not even a problem at all, and it might not even be technically an obsession, but the narrative treats it like an unhealthy obsession. If the obsessed character starts doing it in their sleep, that's always a bad sign.
While this kind of thing can happen in real life, it's more common among people whose personalities lend them to obsess over things and with things like smoking which are actually addictive. In some darker works (and darker episodes of usually-light works), the trope may be justified by having the thing turn out to be literally addictive and/or a Mind-Control Device, usually with negative side-effects too (like it tampers with your ability to reason). Sometimes they have a reason for obsessing over it beyond "I want to do it a lot" or "the thing is literally addictive"— maybe they want to become really good at it or win a prize or something.
If the thing the character is obsessing over is a video game, they'll often have everything remind them of it, and when they're trying to give something up, whatever it is, they are often reminded of it by things that would remind anyone of it, such as ads for it. If they have to give it up completely and it's the "not really an obsession but the narrative treats it as one" variation, then it's also an example of Compressed Abstinence. If it involves a song, expect other characters to find it annoying, in an In-Universe version of Ear Worm. If it involves modern technology, expect New Media Are Evil and/or New Technology is Evil to be in play (not always, but most of the time), and if it leads to them losing sleep, it may overlap with Sleep Aesop, especially in kids' shows. See also Anti Poop-Socking when a video game attempts to defy real-life examples of this trope.
It's closely related to Fleeting Passionate Hobbies, but there is a difference: someone with a fleeting passionate hobby need not obsess over the hobby, and sometimes an obsession can stop being an obsession while the passion remains. Can overlap with Does This Remind You of Anything? and I Can't Believe It's Not Heroin! if it's parodying actual addiction, which can overlap with Getting Crap Past the Radar if they parody actual addiction on a kids' work. Also compare Radish Cure which involves convincing someone not to do something by making them do it lots of times so that they'll be bored of it.
- Genesis of Aquarion: One episode has Pierre obsess about "combining" after learning that the woman he likes (their status together is ambiguous) is marrying his older brother. He repeatedly stacks and unstacks cups, lids and unlids a pen, and is too eager to pilot the titular Combining Mecha, but his increased dopamine level is interfering with their Synchronization rate which needs balance among all the pilots. Of course, these are all sexual metaphors. He manages to shake off his feelings before he joined the fight against the Monster of the Week. Before the episode ends, it's shown that another pilot might have picked up the habit.
- The Simple Samosa episode "Toast Malone" is about Dhokla discovering the music of the episode's title character, a Post Malone stand-in, and listening to it in such unhealthy amounts that Samosa tries to get him to stop. Despite his best efforts, Samosa's ideas keep falling flat, culminating in Dhokla selling his house for a pair of golden headphones so he can keep listening to Toast Malone's raps.
- In The Berenstain Bears book "Too Much Internet", the Bear family takes up going online but then spend way too much time online so they decide to only spend an hour a day online.
- The Addams Family:
- In "Morticia the Writer", Morticia takes up writing, but has to stop because she spends too much time on her writing and it interferes with her and Gomez's love life.
- In "Morticia the Sculptress", Morticia takes up sculpting but not only does she end up spending too much time on it and affecting her and Gomez's love life, she also forgets to pay attention to their kids.
- One episode of Brooklyn Nine-Nine sees Capt. Holt getting addicted to a match-3 game on his phone.
- Drake & Josh: The episode "The Bet" revolved around Drake and Josh being addicted to junk food and video games, respectively. After they forget to pick up Megan from a party, the two are both grounded. They then bet each other who can go the longest without indulging in their respective vice.
- In "iStage an Intervention", Spencer becomes obsessed with the old arcade game, "Pak Rat". He spends all of his time playing the game, refusing to even go to the bathroom or do the work he's being paid for. He is only convinced to stop when the kids convince the "Pak Rat" world champion, Sasha Striker, to come and challenge him. At the end, Carly begins to play, and winds up just as obsessed as her brother.
- In "iFence", Spencer teaches Freddy how to fence... and then they both refuse to stop fencing. Even when they're blocking people in the living room or infuriating their friends, they keep practicing, because Freddy turns out to be naturally talented at the sport, and they want to defeat Spencer's rivals. According to Mrs. Benson, this is genetic; Freddy's grandfather was also a talented fencer... but became completely and utterly obsessed, leading to his downfall.
- A recurring plot for Hal in Malcolm in the Middle, to the point where he and Lois have rules about it (i.e. he cant put his job at risk and their joint bank account gets frozen until his obsession runs its course).
- Parks and Recreation, Ben's foray into calzone baking and stop motion pictures.
- In the Star Trek: The Next Generation episode "The Game", Riker comes back from Risa with a game you play with your mind and introduces it to the rest of the crew. This game is literally addictive and leads people to want to get others to play it too. Soon everyone's obsessed, except for Wesley (who did the research and found out what it did) and Data (who's an android), who is "mysteriously disabled". It was a plot by an alien species call the Ktarians who were going to use the game's addictive power to take over Starfleet.
- During the Star Trek: Deep Space Nine episode "Dramatis Personae", while under the influence of some sort of energy spheres Commander Sisko becomes an "Emperor Rudolph-type" tinkerer, fussing over a strange sort of clockwork device that he's building. At the end of the episode, he even admits to Major Kira he has no idea what it is he's built.
- An episode of Victorious had the main characters become focused on their social media followings, to the point that they ignore an assignment for their film making class. They do manage to get over it and finish the project, but the film they made wasn't that good.
- In an episode of The Worst Witch, a few people (teachers and students alike) become obsessed with a game which turns out to have been cursed so that everyone who plays it would be obsessed with it.
- "Play it Again, D.W." involves D.W. playing her favourite song again and again, annoying everyone else.
- In "Binky Barnes, Wingman", Binky takes up butterfly catching and becomes obsessed. Unlike most examples of this trope, he has a clear reason behind his obsession: he wants to catch an elusive blue butterfly.
- In Brandy & Mr. Whiskers, Brandy finds a videogame lost and gives it to Whiskers so he will stop pestering her to play with him. But he becomes obsessed with it, playing nonstop, with the videogame sounds and Whiskers attitute driving Brandy insane. At the end Whiskers learns to calm down (after having to choose Brandy and sacrificing his game) he recites an aesop that no one should stay glued in front of a screen for hours...before remembering he is on TV.
- One episode of CatDog sees Cat becoming obsessed with collecting Mean Bob action figures.
- An episode of Doug called "Doug's Lost Weekend" has him winning a "Super Pretendo" video game system, which he becomes hooked on all weekend and forgets to do his homework.
- In The Loud House episode "The Crying Dame", one-year-old Lily has been crying a lot, so her older siblings give her a singing toy fox to cheer her up. Trouble is, Lily carries the fox around all the time and they find its song annoying, but when they take it away, she gets sad again. Eventually, they solve it by singing the song to her themselves.
- In Madeline, the episode "Madeline and the Ice Skates" has Madeline take up ice skating but it leaves her with no time to play and leads to her skipping meals and staying up late, so eventually she decides to only skate once a week.
- Martha Speaks:
- In "Helen's All Thumbs", Helen plays this video game but gets obsessive and neglects her dogs and homework so she has to give it up.
- An unusual case in "Martha's Dirty Habit", which deals with her digging. She usually digs a lot anyway, but apparently every spring, she becomes more obsessive about it to the point of digging on other properties.
- In the Milly, Molly episode "The Tree Hut", a boy named Maxter watches TV 24/7, which is obviously unhealthy, so the girls build him a tree hut... but then he wants to stay there 24/7, so they decide to teach him sports. He's obsessive about them, too, but at least he's staying active.
- Subverted in the Rugrats episode ""Give and Take": Chuckie spends a lot of time playing with a inflatable bouncing toy called Boppo and it seems like it's going to lead to a "he's obsessed, he must stop" plot when the twins point out that he isn't playing with them and "has a problem", but then it leads in a completely different direction with Chuckie becoming scared of it upon realizing it's a clown.
- In the Spongebob Squarepants episode Have You Seen This Snail? Spongebob becomes obsessed with trying to break The Dirty Bubble Challenge in paddle ball, he does it so much he forgets to feed his pet snail Gary who then decides to run away, after he finally gives up he realizes that hed been at it for weeks and realizes hes neglected Gary so he goes out to find him, which sets up the main plot of the episode.
- In the We Bare Bears episode "Tote Life", the bears get shamed by a grocery clerk for using plastic bags, so they buy some reusable tote bags. This quickly turns into a collection, then an obsession, to the point where their whole cave is filled with bags. Eventually, an EPA agent has to intervene due to their collection becoming harmful to the forest's wildlife. She manages to snap them out of it by pointing out the irony of the situation: the whole point of reusable bags is that you don't need a lot of them, and that they're meant to be less harmful for the environment. In the end, they donate their collection to some nearby beavers as building materials for their dam.
- In the episode "Yakity-Sax" of My Little Pony: Friendship Is Magic, Pinkie Pie develops an obsession with playing an instrument from Yakyakistan called the yovidaphone. She plays it constantly, usually in places where the noise from it causes problems for others. When she's asked calmly to stop playing it so much, she is willing to give it up, but then that causes her to become so depressed her mane straightens and she turns gray like when she was brainwashed by Discord. She eventually moves to Yakyakistan so that she can at least hear others playing the yovidaphone, but that doesn't cheer her up until she's allowed to play the instrument herself again.