I was just reading that ...

Question: I was just reading that Criminal Minds was losing Lola Glaudini after six episodes and replacing her with an older female who acts as a foil of sorts for Mandy Patinkin's character. This got me thinking: Has a show ever brought back a character from a previous show and added them to their cast as a regular? I was thinking along the lines of Ally Walker's Profiler, Dr. Samantha Waters. It seems like an interesting proposal to integrate her into the show, and her character is so similar to what the team does now. I have always liked Criminal Minds (although I know it's not your favorite), but I agree it seems a bit lacking. Anyway, just wondered if anything similar has been tried.
Answer: The most famous example I can think of is Richard Belzer as Det. John Munch, a character introduced on the classic Homicide: Life on the Street who later joined Law & Order: Special Victims Unit after appearing in crossover episodes of the original Law & Order. (The character has also made stunt cameo appearances on cult shows such as The X-Files and Arrested Development, among others.) A colleague also reminds me that Alan Rosenberg and Debi Mazar's characters from L.A. Law migrated over to Steven Bochco's short-lived Civil Wars series. I'm sure there are others, but this is not a good time of year to be throwing trivia questions at me when my mind is about to explode with new TV. As for your suggestion about Ally Walker: why not? She certainly couldn't hurt the show.

(Oops. I should have said that the Civil Wars characters joined L.A. Law after Wars got canceled. A number of alert readers with long memories clued me in Monday as soon as they caught my mistake.)