Real person. Actor, best known for her role in Vertigo (1958).
S3E4 - Joel watches Midge perform in Vegas. The two then hit the slot machines, and spot Kim Novak playing roulette while sharing a drink. Joel successfully steals her napkin as a souvenir.
JOEL: That's Kim Novak? (gasps) That's Kim Novak.
MIDGE: That's what I'm saying.
JOEL: She's playing roulette?
MIDGE: She's so elegant. Should I go blonde again? Oh, my God, Imogene would die if she was here.
JOEL: She'd just keel over and die.
MIDGE: She dabbed her mouth.
JOEL: She's all kinds of human.
– S3E4