I am not sure if this is the right forum for this, but still, here we go.
What are some of your favorite diaper moments in video games that you've played?
These are simple, but for me, two stand out. In Jak 3, for PS2, there is a cheat called "Kleiver's Diaper" that makes one of the main characters, a tough-guy adult, be plainly wearing a diaper. (You can still tell that he's wearing a diaper if you angle the camera a certain way without using the cheat, but the cheat makes it blatant.)
Another are a couple simple lines in the PS2 video game adaptation of the movie Spider-man 2. When Spider-man goes to fight Shocker, one of his allies says something about "kicking is heavily padded butt", and although not a diaper reference per se, well, it sounds like one. The other, when they're fighting, Spider-man asks, "I gotta ask... how's your absorbency compared to other brands?"