More from EW
1 of 13
Cousin Oliver on The Brady Bunch
With the rest of the kids wrapping up puberty, producers on The Brady Bunch decided it was time to debut a new, young cast member: Cousin Oliver. The move, of course, backfired. (Oliver lasted only six episodes, and the show was canceled.) But it did introduce a new phrase into the lexicon: ''Cousin Oliver Syndrome.''
2 of 13
Chrissy on Growing Pains
In its fifth and sixth seasons, the series took a page from a soap opera and decided to insta-age Chrissy six years. Too bad we liked her better in diapers.
3 of 13
Luke on Growing Pains
Yes, they did it TWICE. Before Leonardo DiCaprio was king of the world — or even Hollywood — the actor had a recurring role on Growing Pains. It was still less offensive than the Chrissy gambit because, well, it's Leo.
4 of 13
Stephanie on All In the Family
Season 9 of the sitcom began with the introduction of this tyke, Archie and Edith's orphaned niece. Good effort to mix things up on the producers' part, but the Bunker homestead is not exactly the best place for kids.
5 of 13
Sam on Diff'rent Strokes
When numbers for this once-top-rated sitcom began to sag, producers brought in Sam, Mr. Drummond's new stepson. The bratty Sam was so reviled, fans cheered when the character was kidnapped in a very special episode, thinking he was about to be written off the show. What were the showrunners talkin' about, Willis?!
6 of 13
Maddie on Ally McBeal
We loved Ally because she was a singleton. But then the show's producers decided to introduce an unnecessary family-oriented plotline by debuting Maddie, a young girl who claimed she was Ally's daughter. Sure, the show gets props for casting a young Hayden Panettiere in the role, but Ally McBeal was better without a baby. Unless it's dancing, of course.
7 of 13
Olivia on The Cosby Show
Rudy Huxtable was cute. Unfortunately, Olivia — Denise's stepdaughter, who was introduced in season 6 — was just a pale imitation. Not even an awesomely bad sweater would save the character.
8 of 13
Billy on Who's the Boss
During the seventh season, showrunners decided Tony Danza needed another comic foil. So they added Billy, a cute young kid from Tony's Brooklyn neighborhood. There's only one problem: Tony already had a foil — Angela. Good thing the newbie only lasted one season.
9 of 13
April on Gilmore Girls
Just as we were beginning to think Luke and Lorelai were finally happy, Gilmore Girls introduced yet another reason for them to argue: Luke discovered he had a daughter, April. Suddenly, the show began to focus almost solely on the dynamic between dad and daughter. And last time we checked, the show was called Gilmore girls.
10 of 13
Andy on Family Ties
Let's face it: Family Ties was all about Alex P. Keaton. So did we really need another cutesy boy added to the cast?
11 of 13
Ricky on The Partridge Family
We could hardly come on and get happy about Ricky, the precocious neighbor added in season 4 after David Cassidy left the show. If we wanted to hear children's music, we would watch Sesame Street, thankyouverymuch.
12 of 13
Daniel Jr. on Ugly Betty
We said ''non, merci,'' as soon as Betty decided to debut Daniel Jr., the orphaned French son the Mode editor never knew he had. The show already has one button-cute youngster (Hello, Justin!). We didn't need another. Especially one with a horrible French accent.
13 of 13
Scrappy-Doo on Scooby-Doo
In the late 1970s, the cartoon began fielding cancellation threats. So what did they do? They added Scrappy-Doo, Scooby-Doo's pugnacious — and extremely obnoxious — nephew. To the show's credit, their ratings did increase, but, creatively, we still think the move was one big Scooby-dooby-don't.
For more on TV's biggest blunders (Jay Leno in primetime!) and bombs (Cop Rock!), check out the new issue of Entertainment Weekly