AUNT PETUNIA
Oh no. Oh no. What have you done? You’ve wet the bed, again.
She pulls back the covers.
This is very unacceptable.

YOUNG HARRY
I’m... sorry, I think I was having a nightmare.

AUNT PETUNIA
You disgusting boy. Only animals wet themselves. Animals and disgusting little boys.

Harry Potter and the Cursed Child - Chapter 2 :
See this quote in the Pensive -