S4, E11: As Charlie prepares for a steamy Christmas Eve alone with his date, his friends and family keep dropping in--and staying--until Charlie finds himself hosting an unplanned, unwanted holiday party. Upon discovering whom Charlie's new girlfriend is, Evelyn inexplicably becomes desperate to break them up before they go too far in their relationship. Susan Sullivan ("Dharma & Greg") guest stars as Dorothy, the mother of Charlie's date. Recurring guest star Ryan Stiles appears as Judith's fiancée, Herb.