Did anybody else ever wonder why Sondra & Elvin were featured in the opening credits, despite the fact that they were clearly not "regulars"? In pretty much any other series, if you're featured in the opening credits then you appear in pretty much every episode. Sondra & Elvin were, in my opinion, what they call "recurring" characters, meaning they were a major part of the show, but they only appeared every 4-5 episodes at most.

I also thought it was kind of silly that Sondra & Elvin moved back in with Cliff & Clair during season 8, and then continued to only appear every 4-5 weeks. That plot development made no sense to me...

I don't understand either.

For 227, I do not understand why Calvin and Pearl were NOT featured in the 1st season's opening credits. ThomasE said that in the 1st episode, they did not act that they seemed to be related..

I always wondered that also

I really don't have an answer for that question. The Grandfather was on just as much as Sondra and Elvin, maybe even more and he wasn't in the opening credits.