Note that Robert Reed, a.k.a. Mike Brady, never appears in "The Brady Bunch" final episode, even though son Greg is supposedly graduating from high school, and his devoted dad would have most definitely been there.
Reed, who had Shakespearean training (although he also appeared in a movie that made "Mystery Science Theater"), was known for protesting the slapsticky "Brady" humor, and the last episode pushed him too far. You remember it -- Bobby sells hair tonic, dyes graduate Greg's hair orange, then sells orange bunnies, cousin Oliver wanders about randomly.
Anyway, this blog links to Reed's overheated memo about why the episode sucks.
I just think that instead of inserting a throwaway Carol line about Mike being out of town, they should have said he was unloading the car, or picking up a cake, or something. That always bugged me. (Via Boing Boing.)
Update: Rob points out that Robert Reed wasn't too high-and-mighty to skip doing the Brady Bunch Variety Show, which included the oh-so-realistic concept that an architect and his family would get a variety show of their own that for some reason involved synchronized swimming.