1. Was Danny's mom originally intended to be a recurring character?

2. Why was Alice Hirson subsequently replaced by Doris Roberts?

http://whatculture.com/tv/10-characters-famous-tv-shows-swept-carpet.php/5

1. No I dont think she was supposed to be a regular. She only appeared once after the first episode. And that episode was all for the purpose of being about the guy's mothers.

2. Well it had been 2 years since the original actress had played Claire Tanner, so it's very possible they had plans on bringing the same acress back but she declined and was busy with other things.

I will admit tho, they could have done a better job at making the 2nd Claire more like the first one. But I did enjoy the 2nd Claire. She really did have more of a "grandma" vibe to her.