My son was a week away from turning 3 and would sit on the potty when he felt poo-poo was coming, but then it wouldn't come. I'd put his diaper back on and it would come! It was a just a "thing." The day before he turned 3, Grandma visited from Arizona, and had a squirt gun to give him - - but only when he made poo-poo in the potty. That first day, I gave him "naked time" out on our back patio with his sand-box and wading-pool. Grandma and I sat on the porch swing and talked and watched him play - - until he said he had to go! We ran in to the potty when he felt it coming - - NOTHING! We came back outside. It was coming! We ran back to the potty - - NOTHING! We came back outside. Next time, it was coming, I didn't think it really was, so I said, "Oh, just squat over there and put the poo-poo in your yellow sand-bucket." IT CAME. We called his dad and celebrated, but dad was doubtful and said, "What if he goes to college carrying a yellow, sand-bucket under his arm?!!"
The next day, my son was calling from the potty, "OH, Grandma! Can I have my squirt gun now?!" He had the biggest grin on his little face when Grandma acted all surprised and happy that he had put poo-poo in the potty.
I waited 15 years to be able to do the punchline to this story. When my son left for college, I handed him a large industrial-sized yellow, sand-bucket with a list of the top ten uses for it at college!!!!