You know them, you loathe them. They are the unnecessary, obnoxious and often just plain annoying mid-series additions to established shows. Sure, there are times when a compelling, fresh-faced character is introduced and breathes new life into a series. Unfortunately, those instances are few and far between. Like with most of the television industry, the bad in this case far outweighs the good.

What follows is a list of the worst cast additions** in the last 30 years. Each and every one of the characters mentioned below was detrimental to the series in which he or she appeared. Some of the additions fall into similar categories, and are grouped together thusly.

**We were tempted to construct this list by using the famous "show destroyer" Ted McGinley in every series where he made an appearance, but that would have become a little redundant.

The "replacement for cute kids who were no longer cute" all-stars

Olivia – The Cosby Show; Andrew – Family Ties

It’s truly a day of mixed emotions for sitcom showrunners when they realize that the youngest child in their cast has grown out of his or her "prime cuteness stage." On the one hand, it is a sign that the series has been around long enough to have a one time six-year old approaching puberty. However, it is also a stressful time because the "cute kid" is often a vital part of the family sitcom formula. In those situations, there is only one clear cut answer: bring in a new kid! Younger and cuter! Unfortunately, it rarely has the intended impact on the show.

Olivia (Raven-Symone) was brought in to pick up some of the cuteness slack dropped by the aging Rudy (Keshia Knight Pulliam). What viewers ended up receiving was a syrupy sweet overload of the annoying three year old, a character that seemed to appear more often in later seasons than a majority of the pre-established regulars. The desire to add a young kid to an aging cast is understandable, but it should not be done at the expense of other, stronger characters who actually add some value to the show. Smiling, looking cute and exasperating Bill Cosby does not count as value. Sorry Olivia.

"The Cosby Show" was not the only culprit from NBC's mid-80s Thursday night lineup. "Family Ties" actually encountered the problem sooner, because the original designated cute kid was already nine years old when the show started. After the first couple of seasons, it became apparent that a replacement was needed. Enter Andrew.

At first, when he was in baby form, Andrew was tolerable. But then a young Brian Bonsall took over, and it was all downhill from there. There have been a lot of bad child actors throughout the years, but none could match Bonsall’s excruciating performance as the young Andrew Keaton in "Family Ties." Thankfully, he was only around for a few years before the series was mercifully canceled.