Cliff's overprotective mother. It is first mentioned in Season 3 that Cliff lives with his mother, which the other barflies often mocked him for. In the episode "Coach in Love Part 2" (Season 3), Cliff's mother is first heard in a voice-over at Cliff's house. When she asked if she could stop by and meet the gang, Cliff whispered under his breath "When hell freezes over". Despite that, Esther showed up at the bar in Season 5, when Cliff tries to set her up with a wealthy Cheers patron. She appeared numerous times afterward, through the final season.
In the episode "Last Angry Mailman" (Season 6), it was revealed that Cliff, contrary to his usual know-it-all personality at the bar, is actually quiet at home, and his mother is actually "the real yapper in the family". Cliff, after listening to his mother drone on and on, when he arrives at the bar he shares his mother's knowledge with the gang, giving them the idea of Cliff's infamous know-it-all personality.
Esther Clavin was played by Frances Sternhagen.