Of the four girls, the ones where one didn't appear were and also if anyone knows the behind the scenes reasons if any and charachter expinations:
Jo of course wasn't in the 13 season 1 episodes and missed two I believe at the start of season 6 in a contract dispute. which tow were they as they were the first two produced not aired, and was her charachter mentioned as being away?

Tootie I believe was in every episode except the one where Jo's dad meets Rick for the first time.

Blair was in every episode except the First Time due to her religous beliefs. i don't think her charchter was mentioned as being away or anything.

Was Natalie in every episode? I think in the last one she called from SoHo in the begining.

Natalie was missing from the Blair's 21st Birthday episode. Reference was made to her being out of town.

Wasnt Nancy missing from a few due to contract squabble maybe season 5 or 6? I think they just said she was visiting her mom or something like that

Yes, Nancy missed two when she was renegotiating a raise/contract dispute but I don't remember what two they were.

Blair was in every episode except the First Time due to her religous beliefs. i don't think her charchter was mentioned as being away or anything.

Jo makes some remark about it being quiet because Blair is not there.

D

I'd like to bump this one to ask: When did Jo walk out from the show?

Also: While I was looking through tv.com to see if I could find anything about Jo being absent, I see that there were 2 episodes Mrs. Garrett didn't appear in: "Sisters" and "It's Lonely At the Top", Mar. 20 and 27, 1985.

OK, now I know when Jo walked out from reading an earlier post here:
The 1st 2 episodes of Fall, 1984.

Nancy and Lisa's absence was explained but why did Kim and Mindy miss an episode?