Dinner at Eight-ish Cheers : Season 5 Episode 20

Frasier and Lilith invite Sam and Diane over for dinner to celebrate their first week of cohabitation. But things start going wrong when Lilith finds out Frasier and Diane were engaged, and she locks herself in the bathroom. Then Sam and Diane have an argument as well. Meanwhile Cliff agrees to babysit Carla's kids.