Potty Training Fun!

Taben's over 3 now, and I'm having a heck of a time potty training him! He knows how to go, and when he has to go, but he refuses to go in the potty, he'd prefer to go in a diaper/pull up. It's driving me crazy! So the other day I decided that if he poops, then i'll flush it down the toilet so that he knows it's ok for it to go down the toilet and not to be scared. So the other day I put it in the potty when I was changing him, and told him to say "bye poop" so he did, and I flushed it down and was telling him how it's ok for it to go down the toilet. He then asked me, "Where's it go" and I said, "In the sewer". He then thought a sec then replied, "and then do hippos eat it?" Oh my gosh! I just stared at him and then busted up laughing! It has to be one of the funniest things he's said!
The next day (this was now yesterday) on the way home from day care, he asked me where his potty was (he has his own potty that I haven't put out since I moved back into my parents house) so I decided it get it out and see if maybe I'll have more success trying to get him to go potty. I set it at the foot of the stairs, and then had him come help me do some laundry real quick. He left the laundry room after helping put maybe 2 things in the washer, and then was out of the room. When I got done I came out of the laundry room and found Taben with his pants down with his diaper off, and sat down on his potty! Well, I guess as long as he gets the concept it doesn't matter where the potty is huh? Haha. It was too funny! He used his potty a couple of times yesterday, then hasn't wanted to use it since! Grr. Eventually I'll find some method that works!