The Bewitched x-over was because it was on the same network as the Flintstones (ABC) and from the same parent studio (Screen Gems). Gerry Johnson (Betty) appeared on Bewitched during its 1st season. You'd have to look quick, as she appears at the end of "A Vision of Sugar Plums" w/Bill Daily to adopt Bill Mumy's character. So, Dick York & Elizabeth Montgomery agreed to return the favor and do the x-over the following season.