At the restaurant, while the Cleavers are debating the Beaver's promise to eat his Brussels sprouts, his crumpled napkin falls off the table. It suddenly appears, nicely folded, in the very next Beaver shot.
June makes a big thing about Beaver's not eating the Brussels sprouts and leaves him alone at the dinner table to finish them. June then goes into the kitchen to wash the dishes and every plate she scrapes off seems to have uneaten Brussels sprouts on them.
At the restaurant, the ladies sitting behind the Cleavers included Sue Randall, who plays Beaver's teacher, Miss Landers. No one acknowledges this at all.