I have read some interesting stories about them. They have all been verified too.
One is that the first time Florence kissed Mike, during the first filming. She came to the producer and said, “This guy ain’t straight. Later Sherwood Schwartz confirmed that she did. It was surprising to me that she could tell just from a screen kiss.
Another one was that Henderson walked around topless during backyard parties. She had a high fence so no one else could see.
Third was confirmed by both Greg and Marcia. She was visiting him and they were swimming in his parent’s pool. After a while they went up to Greg’s room. They eventually got naked and were just about to hit a home run when Greg’s Father got suspicious and knocked on the door. They hurriedly got dressed and never got together again.
In my mind I'm picturing Sam the Butcher pounding on the door.