15/28) Danny Rubin and Harold Ramis both said that they purposely avoided exploring the truly dark side of Phil's time lapsing in which he could do truly horrible things without consequence (i.e. murder, torture, etc.) to maintain a more lighthearted feel.
16/28) Bill Murray was undergoing a divorce at the time of filming and was obsessing about the film. He would ring Harold Ramis constantly, often in the early hours of the morning.
Ramis eventually got tired of it, and sent writer Danny Rubin to sit with Murray and iron out all his anxieties, one of the reasons why Murray stopped speaking to Ramis for several years.
17/28) In the original version of the script by Danny Rubin, Phil Connors was already trapped inside Groundhog Day at the start of the story. We joined him on a typical day, with the audience wondering how he knew everything that was going to happen.
Harold Ramis promised that he wouldn't change this aspect of the script, but ended up changing it anyways.
18/28) Supposedly Paul Lynde was the inspiration for one of the film's more famous lines: After a high-speed chase through the San Fernando Valley one night when he was driving recklessly while intoxicated, Lynde crashed his car into a mailbox. The police came to the car, guns drawn, and he lowered his window and said, "I'll have a cheeseburger, hold the onions, and a large Sprite."
19/28) The groundhog ceremony is depicted as occurring in the center of town but in real life, Gobbler's Knob, where the ceremony takes place in real life, is a rural, wooded area, about two miles outside of Punxsutawney.
20/28) A family of groundhogs was actually raised for the production.