Ken Osmond (John) had previously played Eddie Haskell in Leave It to Beaver (1957), whose creators/producers Joe Connelly and Bob Mosher also produced The Munsters.
Another connection to "Leave It To Beaver" - the sorority is named Alpha Kappa, which was Ward Cleaver's fraternity in college (season 6 - "Wally and the Fraternity".
Michael Blodgett (Jim) was cast in the TV Movie Meet Me in St. Louis (1966), a pilot for a series based on the original 1944 MGM film. It was a non-musical version starring Shelley Fabares in the role of Esther, previously played by Judy Garland. Unfortunately, no network picked up the project as a series.
In the episode Herman's Sorority Caper, Grandpa is shown looking at himself in a mirror, but vampires can't be seen in mirrors.