Bob was supposed to be a swinging bachelor, but he lives with his sister? Doesn't really make sense.
The other thing is, he does these ridiculous episode playing his Grandpa. Well, since Cummings was around 50, his grandpa would have been in his 90s.

Bob was in his 40s for the entire run of the series.

Bob was supposed to be a swinging bachelor, but he lives with his sister? Doesn't really make sense.
The other thing is, he does these ridiculous episode playing his Grandpa. Well, since Cummings was around 50, his grandpa would have been in his 90s.

It's funny you should mention that episode, he tried to resurrect the Grandpa character on the series My Living Doll. A poster who billed himself as TV Knowledge Fan posted this information a decade ago about the incident:

Bob Cummings "walked away" from the series in January 1965 due to the friction caused by a script Cummings commissioned from Ray Allen (Saffian), which would have been the 22nd episode to have been filmed, "Grandpa Visits". This episode would have introduced "Grandpa McDonald"- virtually the same character {"Grandpa Collins"} Bob had played on his earlier series. When executive producer Jack Chertok read the script, he was furious, because Julie Newmar had been literally written out of the story ["Rhoda" would have appeared only briefly, at the beginning and end]. He called Bob into his office for a meeting, and let him have it. Chertok reminded Bob that this was "MY LIVING DOLL", not "THE BOB CUMMINGS SHOW", and that Julie was his co-star. He wasn't going to stand for Julie being off-camera for almost an entire episode {there was already tension behind the scenes between Bob and Julie, because, among other incidents, he tried to "teach" her how to act}, and he certainly wasn't going to indulge Cummings by allowing him to revive a character from his previous show. After the meeting ended, Bob decided to leave the series....Jack Mullaney became Julie's co-star for the final five episodes.

TV Knowledge fan was a great poster full of inside information, unfortunately he hasn't posted here in about 10 years.

Cummings was a giant pain in the ass and Chertok had wanted Bob Crane for the part but CBS forced him to use Cummings. That may explain why Chertok had such bad feelings about the show and had all of his films and negatives destroyed.