Lola mentioned Walter and Patricia in The Shelf.
In You've Got Hate Mail, Walter invites Bugs to be in his family photo.
Walter then returns in Rebel Without a Glove. Here, Bugs goes through a personality change, which causes him to become a gangster. Walter disapproves of this, and forbids Lola to go out with Bugs. After Bugs gets back to normal, he allows Lola to go out with Bugs again.
In Father Figures, Walter enters a father-son tennis tournament with Bugs. But, first, he and Bugs must have some "special bonding."
Walter and Patricia made a cameo in A Christmas Carol.
Walter appears in The Black Widow.