“I brought a package of diapers just in case, and seems I made the right decision!“

“Pinkie!“

“What? It seems you’re about to have an accident. It’s been ages since you took a bathroom break, and we won’t be able to take another one in a long while.“

“Don’t mention it!“

“We should start now. You don’t want to piddle all over your seat, huh? Don’t be a silly filly and get in the changing station! It’s never out of order.“

“Grumble… make it quick.”

Alternatively: “I have packages of diapers hidden all over ponyville, you never know where a potty emergency will happen!”