Someone HELP!

I am beginning to wonder if Doster will ever be potty-trained. He does a great job when I prompt him and when I take him to the bathroom. If I don't suggest it, he NEVER tells me and will easily go in his pull-up, underwear or diaper. I have tried leaving him in the mess to teach him the discomfort - doesn't work. I've tried making it really exciting and rewarding - doesn't work. I've even tried, in desperation, a spanking and time-out which are supposedly big no-no's - they don't work. Anyone have any ideas? If so, feel free to send them our way!
These pictures perfectly depict his attitude towards potty-training...he has so many better things to do, places to go, fun to have, and would much rather be making someone laugh.