They Wasted Three Days Of Shooting
In a scene that was eventually cut from the film, Murray’s character, Phil, gives himself a mohawk, paints his room, and goes crazy with a chainsaw. Filming for the scene took three days even though none of it made it into the final cut.
However, instead of being ultra-destructive, director Harold Ramis had Phil just break a pencil only to see it appear whole again the next morning. This scene helps audiences realize what exactly is going on in a much more subtle way than using a chainsaw like they originally planned.