It seems that the vast majority of television shows’ closing themes (i.e., the music played over the end credits) are instrumental. If the opening theme has sung lyrics, then the closing theme is usually an instrumental version of the same theme. If the opening theme is itself instrumental, then the closing theme may be the exact same music, or maybe a slightly different recording of it.
What are some notable exceptions to this general rule? That is, which TV shows have closing themes with sung lyrics?
The only one I can think of offhand is Frasier. This show doesn’t have an opening theme as such—just a title card with a brief musical cue—but the closing theme is a song, “Tossed Salad and Scrambled Eggs”, sung by Kelsey Grammer.
The first season of Simon & Simon played an instrumental version of the theme song for the opening credits, and a sung version for the closing credits. “Best of Friends” written by Barry de Vorzon and Linda Creed, performed by the Thrasher Brothers.
In the second season they replaced it with a different song (also by Barry de Vorzon), instrumental for both opening and closing.