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Harold Ramis has stated that the inspiration for this movie was not the novel "The Strange Life of Ivan Osokin" (1905) by P.D. Ouspensky, but many others think that it was. Ramis made this denial within his contributions to a jacket blurb for one edition of the Ouspensky book. In the book, Osokin is given the opportunity to live his life over again by a magician... and Osokin takes him up on the offer, only to make the same mistakes all over again. Eventually he reaches the point in time where he met the magician, who explains to Osokin that he cannot change the recurring wheel that is "this trap called life," and that Osokin must learn to sacrifice, in order to escape it, to find his salvation.
Bill Murray was bitten by the groundhog twice during shooting. Murray had to have anti rabies injections, because the bites were so severe.
According to Director Harold Ramis, most of the time, when he tried to explain a scene to Bill Murray, Murray would interrupt and ask, "Just tell me - good Phil or bad Phil?"
Harold Ramis originally wanted Tom Hanks for the lead role, but decided against it, saying that Hanks was "too nice."
(at around 59 mins) The scene where Phil picks up the alarm clock and slams it onto the floor didn't go as planned. Bill Murray slammed down the clock, but it barely broke, so the crew bashed it with a hammer to give it the really smashed look.
The film was not filmed in Punxsutawney, Pennsylvania, but actually in Woodstock, Illinois (just fifty miles from Bill Murray's hometown of Wilmette, Illinois). There is a small plaque that reads "Bill Murray stepped here" on the curb where Murray continually steps into a puddle. There is another plaque on the building wall at the corner that says "Ned's Corner" where Phil Connors was continually accosted by Ned Ryerson. During the Ned scene the sign for "Woodstock Jewelers" is clearly seen in the background.