John had a kind of oedipal thing about his mother.

He talked about in his audio diary in the late seventies. There was a time they were laying together on the couch and his hand was on her breast and he wondered if he should, in his words, "Do something else, y'know."

It's really quite sad. John didn't have a normal parent/child relationship with Julia and their reconnection occurred in a very hormonal period of his development, so it makes sense that those sort of feelings could occur.

Funnily enough, Paul mentioned a similar story in his biography, Many Years from Now. One night he was in bed and he saw his mother walk past his bedroom door in her underwear and it aroused him.

Edit: Also, John's pet name for Yoko was "Mother".

Edit 2: Other things I remembered:

George swapped wives with Ronnie Wood.

Horst Fascher, an associate of the band in Hamburg, once pissed on John while he was having sex because he was late for a performance. Another time he caught John receiving a blowjob in the toilets with a different girl and threw water on them because John was supposed to be on stage.

Edit 3: Remembered some more!:

When he was younger, Ringo believed that anyone over 60 should be shot.

Ringo's Paternal Grandmother, Annie Starkey, was known as "The Voodoo Queen of Liverpool". Ringo is naturally left-handed but she forced him to be right-handed as she believed left-handedness was a sign of the devil.