Game: Duck Hunt
Character changed: Duck Hunt Shooter (OC of the character you play as in the games)
Method: Shoot the dog intentionally to the point where it gets annoyed by your actions
Link to Contest Journal: https://tf-tg-contests.deviantart.com/journal/GAME-OVER-Contest-696161663
So here the duck hunter himself has been transformed into another Duck Hunt dog, because if I was that dog and I kept getting shot at, I'd get pretty annoyed too XD. When I heard about the contest, I went straight to making a Duck Hunt based TF but my initial idea was turning the shooter into one of the ducks. However, after doing a few test sketches with some difficulty, I decided it would be much for fun for the shooter to become another DH Dog, forced into a new role as the one picking up the ducks instead of hunting them.
Entry to TF-TG-Contests on DA, thanks for the chance :D