Stuntman Jeff Dashnaw took on the film as a longtime friend of Alan Autry, and created his character on the spot when, sifting through the costume pile (costumes were in the "Saloon"), he bypassed the cowboy hats and grabbed a slightly-small derby hat. Within minutes he was the menacing Crazy Kelly.
In the film, you'll see stuntman Dashnaw riding into town, and at one point his horse quickly lunges towards a young boy. That moment wasn't planned, and the young boy (who happened to be Dashnaw's son) wasn't acting when he got scared and yelled "HEY!"
Alan Autry last played with David Hart (Sheriff) in the "In The Heat Of The Night" TV series.