When we were potty training our eldest son (now 3 1/2 yrs), we used to sit him on the toilet and say "just do your best", even if he went or not, we would praise him, using "well done", etc...
So, once he started to get the hang of it, when he indicated that he needed to go, we'd set him up on the seat, and then he'd say "Daddy, I'll do my best"
Then, at the airport earlier this year, waiting for a flight to arrive, he tells me he needs to poopoo, so I take him to the bathroom, set him on the seat and wait...he looks at me and says "Daddy, I am going to poopoo, OK? I'll do my best and when I've finished, you say "well done" to me, OK?"...
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One of our very good friends has a 5 yr old son. Since him and his elder sister were young, the parents have had no qualms about calling their respective private parts by their normal names, and the state of excitement in the boy termed "asleep" or "awake"
One evening, they are fooling around close to bedtime and his mum asks him if his penis is awake or asleep...
His response: "It's asleep. And do you know why? Because it's bedtime and it's a good penis"