Just stumbled on this episode of the Donna Reed Show from 1960, right about the time Season 2 of Dennis the Menace started. Dennis and Mr. Wilson both make guest appearances in the second half of the episode as part of a rare crossover between shows on different networks (Donna Reed on ABC, DTM on CBS).
Anyone in the know more than me have any idea how this came about? It seemed very random.
I don't remember there ever being any crossovers on Dennis the Menace itself, or it being used as the launching pad for any other series.