You just keep the fight up. It's definitely a phase albeit a really annoying one. I definitely agree with the "fold" trick. I used to do it with DD when she would try to be silly by sitting backwards. Just be firm and tell him that no matter what kind of fit he throws he will get in his seat and be safe. I turned DD at almost 3 bc I was getting frustrated. It worked for maybe a few days then she was just jumping around the car which was harder to deal with. Good luck!!
Anna - SAHM and doer of all things. Loving life with my beautiful girlfriend and our amazing daughter.