Creator's Pet

Sergio

A Creator's Pet is a character that is hated by the fanbase of a particular work, but ends up taking up a lot of screen-time.

The criteria for being a Creator's Pet is that the character must be:

A) Hated by the fans

B) Loved by the production team

C) Shoehorned into a lot of scenes

D) The other characters constantly praise them, even when they don't deserve it.

A Creator's Pet is more often than not a Mary-Sue, that is to say, a self-insert who is highly unrealistic and has no flaws whatsoever. They can also be a Cousin Oliver, a kid who is inexplicably added to a work's roster to liven up an aging cast, named for Cousin Oliver from The Brady Bunch.

Examples

 * 1) Elmyra Duff from Tiny Toon Adventures, the counterpart to Elmer Fudd, was shoehorned into Pinky and the Brain at the request of network executives. She was hated and the show was canceled as a result.
 * 2) Chloe Carmichael from The Fairly OddParents, a complete and utter Mary-Sue, and the third character added to the main cast to boost ratings, after Poof and Sparky. She only exists to make Timmy look bad, and has an incredibly contrived reason to have fairy godparents.
 * 3) Sparky also from The Fairly OddParents, was also added to liven up the cast. He was hated due to being annoying and shoehorned in. He was removed after season 9 ended.
 * 4) Michelle Tanner from Full House. Even though she was there since the beginning, as the character grew, she began to get a lot of screentime and marketing, sweeping all the other characters to the wayside.
 * 5) Wesley Crusher from Star Trek: The Next Generation. He is a Gary-Stu and is a walking deus-ex machina who always saves the whole ship at the last minute. Thankfully, he was kicked off the show after an incident where he inadvertently killed one of his classmates.
 * 6) Scrappy-Doo from Scooby-Doo. He was incredibly annoying and took screen-time away from other characters, mostly Fred, Daphne, and Velma. He was added to boost ratings, and it somehow worked. In later installments of the franchise, Scrappy is made fun of or is an outright villain.
 * 7) Steve Urkel from Family Matters was slated to appear in only one episode, but due to his popularity, he began appearing in more and more episodes until he eventually took over the show, becoming its main protagonist.
 * 8) PinkAru from Tooba Tooba Noonbory, the Korean-exclusive second season of Noonbory and the Super Seven. She's a token kid character who only exists to appeal to younger audiences and her crying is incredibly annoying. She also shoves a lot of characters, such as Totobory, to the wayside.
 * 9) Chibiusa from Sailor Moon, similar to PinkAru, is a pink kid character who only exists so that little kids can relate to her. She was rather unpopular with Japanese audiences, at least in the anime. In Sailor Moon Crystal, however, the reception of Chibiusa is more positive since her personality here is closest to how she was in the manga.
 * 10) Cousin Oliver from The Brady Bunch, who was added in the last six episodes as the cast was growing old.
 * 11) Dil and Kimi from Rugrats, who helped dumb down the show from an all-ages affair into a borderline preschool show when they arrived.
 * 12) Mindy Melendez from Ready Jet Go!. Even though she was there since the premiere episode, she wasn't always there in development, only being created when the crew realized that they needed to appeal to younger audiences. Mindy was very popular with the show's target audience, but in season 2, she started to get all the screentime, promotion, and focus, especially since she turned five and finally got to go to space with the older kids. She was very annoying, a walking deus-ex machina, and often bullied others with no repercussions (such as when she triggered Sean's PTSD in "Galileo, Galileo!). As a result, she became the most hated character in the fandom.
 * 13) Jeffy from SuperMarioLogan is an Evelinka Puppet who was added in 2016, and immediately became controversial and hated for his annoying behavior, innapropriate jokes, and swearing habits. Still, he became an very frequent main character in 2017 onwards.
 * 14) Abby Anderson from The Last of Us Part II, a political soapbox character who kills Joel from out of the blue and never gets killed by Ellie in the end of the story.
 * 15) Elmo (Sesame Street)
 * 16) Abby (Sesame Street)
 * 17) Sergio from The Casagrandes, although he always was apart of the show, he is always shoehorned into scenes and some episodes