The "big shoes to fill" underachievers

Stephanie – All in the Family; Joe Fontana – Law & Order

Being the designated replacement for a popular departed cast member is a tough task, and things certainly aren’t made any easier when the new cast members are dull and unlikable. Enter young Stephanie (Danielle Brisebois) in "All in the Family" and Joe Fontana (Dennis Farina) in "Law & Order."

Rob Reiner and Sally Struthers departed "AITF" following season eight. That left Archie (Carroll O'Connor) with no "Meathead" to kick around, but more importantly it cut the main cast in half. The solution? Add a bratty kid to the mix. Stephanie was pretty worthless as a character in her own right, but the fact that she was technically a replacement for the entertaining combo of Meathead and Gloria made the swap all the more frustrating.

Things were even worse for Dennis Farina, whose character Joe Fontana was given the unenviable task of following the enormously popular Det. Briscoe (Jerry Orbach). Fontana was a dull and humorless character, and he quickly made viewers long for the days of Briscoe and his sarcastic one-liners. Thankfully, due to the revolving door policy that has long been employed by "L&O," Fontana lasted just two seasons.

The "why is she still around" mistake

Meredith Peters – Boston Public

Meredith Peters (Kathy Baker), the unstable mom, first made several guest appearances during season one. Her character was repulsive and unbelievably boring in her few episodes, so what was the solution? Make her a frickin' regular in season two! David E. Kelley has had a long working relationship with Baker, so maybe that’s why he defied all logic and devoted way too much screen time to the terrible character in season two. Whatever the reason behind it, her casting was a disaster and a portent of things to come for the once captivating series.

The "last desperate attempt to save the show" failure

Luke – Growing Pains

Before Leonardo DiCaprio became established as one of the most talented actors in the industry, he was just a struggling teen looking for steady work. For that reason, it is hard to fault him for accepting the role of Luke, the vagrant who is taken in by the Seaver household in the show's last season. It is not at all hard, however, to fault the writers for conceiving this useless character or for imposing him on the dwindling viewer base throughout the entire painful seventh year of the once formidable sitcom. Just a quick tip: when a show is running on fumes, adding a brand new character will not magically invigorate a tired writing staff or bored actors.