I used to mix it in with fried rice that'd been left sitting out for too long and turned really dry. Gives it some moisture and a vinegary edge, but probably not for everyone, since ketchup's trademark is stomping all over the subtle flavors of a dish.
When I was in elementary school, I'd dip my pizza crusts in ketchup at lunchtime. I still do that every now and then with Sriracha ketchup
Also, same elementary school lunch: on pizza days, they also used to give us a side of tricolor fusilli straight-up. Just plain pasta without even so much as a little olive oil. So, fuck it. It got blasted with 'chup.
If you're into the '90s extreme aesthetic, I'd definitely recommend Comix Zone to get you neck-deep in it.
You play Sketch Turner, a comic artist who- along with his pet rat, Roadkill- gets sucked into his own comic by the comic's villain, Mortus, who wants to trap Sketch forever so he can exist in the real world or something.
It's a side-scroller beat 'em up where you move across the panels and pages of a comic book, punching and kicking mutants while the Sega sound chip blasts (occasionally grating but still awesome) grungy rock at you. If you're into '90s shit, there's nothing not to love