In the 2021 movie Licorice Pizza by Paul Thomas Anderson, the main character Gary makes an awkward joke that, as far as I could understand, goes like this (not verbatim):
(on the TV show stage)
Host: How are things going for you, Gary?
Gary: Last week I did three beavers.
Host: You mean Leave it to Beaver?
Gary: Three beavers.
Can someone explain to me as a non-native English speaker and non-American what Gary is referring to here?