Except for her role as Lumpy Rutherford's mom on Leave It To Beaver.
I'm 99.8% sure that you're joking, but I'm still going to have to go look it up now.
Oh no, you weren't joking! So, Majel was like 28 when she played Lumpy's mom, so Gwen must have had Lumpy when she was..what, 13? Well, Fred always struck me as being kind of a creep, this just confirms it.