Potty Training

My son is almost 3 and a half years old. Thus far he has show NO interest in potty training. Previously when I put him in underwear or talk about going pee pee in the potty he would scream and yell. I have tried to be very patient with him and not force the issue. This is a hard thing to do when everyone around him seems to be potty trained. Friends, cousins, fellow sunbeams, everyone! We've been talking about it almost every day. I've tried stickers, charts, candy, trying to get him to pee on cheerios, on food coloring to make the water blue, and watching Daddy. He thinks most of those things are cool, but not quite cool enough to get the job done.
This weekend we went to the store and bought Squinkees. First of all I swore up and down I would never buy a Squinkee, but he LOVES looking at them in the store and I thought it might be just what he needed to try. We were in St. George this weekend and I left Robbie at my Dad's house with my sister and her kids while Rob and I drove Kailyn around trying to get her to nap. My sister called and said that Robbie actually went pee on the potty and was looking everywhere for his Venom Squinkee. I started thinking that I would send him to live with my sister until he came back potty trained because she obviously knew something I didn't know.
The next morning we were back in Las Vegas. I tried to get him to wear underwear but he refused to do it. He likes running around with a "naked bum" so I let him do that. I showed him the potty and told him to let me know when he needed to go. Not much longer he came running over to me and said, "Mom I need my spider-man squinkee." I looked in the potty and sure enough he had gone. Pretty soon he had earned Ironman and the Hulk. Then not much after that he pooped in the potty. He has been doing all of this with no reminder from me. I tried putting underwear on him again and he wore it for a little while and then he had his first accident. For some reason if he is wearing underwear or pants or a diaper he goes in that. But when he is naked he is 100% in the potty.
He might be running around naked until he is 5 but this feels like a huge step in the right direction. The time saved from changing diapers is now spent trying to find the darn sqinkees and making sure Kailyn and Chino don't eat them.