Yes I have peed my diaper on stage.
When I was in 1st grade I was wearing a Pampers Plastic backed diaper under my pants and I had to pee really bad and so I peed the diaper in a flood.
I thought the diaper was gonna leak and so I checked the back of my pants and luckily it was dry.
Those old pampers back in those days were awesome and held a lot.
They swelled up really nice as well.
I also then a few minutes later had to poop and so I let out a large poop in the diaper.
Luckily I was standing in the far back of the stage away from others so they could not likely smell it.