1. Will and Grace- when Grace got married.. the has lost "something"
2. Good Times- when James died
3. Martin- when it was clear that Tisha & Martin weren't getting along and all the shows focused on Martin and Pam
4. I remember back in college when Thursday night use to be the night all of US got together to watch Martin, Living Single, and NY Undercover. I think all three sort of "jumped the shark" all at the same time and then all the scheduling conflicts started. I don't think I've watched TV in a block like that since.