I found this on the internet that I thought was cool:
A trademark of the show is the front door closing magically, which Prue started in the pilot episode. It's been magically closed every season finale ever since.
Season 1 - Prue
Season 2 - Prue
Season 3 - Shax
Season 4 - The Angel of Destiny
Season 5 - Chris Halliwell
Season 7 - Prue (from beyond the grave)
Season 8 - Piper's Granddaughter
With the exception of season 6, when they closed the doors of the delivery room at San Francisco Memorial Hospital where baby Chris was born.