I've noticed that Eddie Haskell does not appear in most of season 2. Does anyone know the story behind that?

I remember we went over this the last time the TVLand run was on season #2, and I think we determined he did not appear at all from episodes #54 throught #78, about 2/3 of a season back then. It is interesting to observe that when he does return shortly after season #3 gets going, he is very noticeably taller and his voice has changed. So it could be that his changing voice was squeaky and he would look like he was growing almost from one ep to the next; and some scenes may have been shot out of sequence.

But it's possible, of course, that all that had nothing to do with it, and maybe Ken Osmond was doing other things at the time. But Wally and Beaver do continue to refer to Eddie, making it clear he is not gone permanently and should not be forgotten.