Wally mentions Cary Grant - Doris Day movies to help Beaver understand his feelings for Penny. This episode originally aired in January 1962, five months before the June 1962 release of That Touch of Mink (1962), the only movie that Cary Grant and Doris Day ever appeared in together.
When Wally uses the Cary Grant-Doris Day example, he's probably referring to Rock Hudson and Doris Day movie pairings. It would be interesting to know if this was an error in the script or Tony Dow's spoken line.