Bastion is incapable of consuming pizza. They've seen other people eat it and they seemed to be enjoying themselves. (In Sail they've had sensory data from eating a couple of meals transmitted to them by a partially organic friend, but that didn't include pizza specifically.)

According to an official shitpost from the then-lead dev all Overwatch characters like/approve of pineapple on pizza and that's the only thing they all have in common, so I guess Bastion thinks the little yellow bits are aesthetically appealing.

Wilson is from before pizza was popular, but it's just within the realm of possibility that he may have had it at an Italian restaurant in the city pre-canon. It's not a consumable food in regular Don't Starve gameplay, but it's one of the seventyish possible meals you can cook in the Gorge event.

Also it's available on the Serena Eterna so he's probably at least tried it in Sail. (In Milliways he can order whatever he wants so he tends to stick to foods he's already familiar with and has not tried pizza.)

Wormwood is from the same canon as Wilson but has never been to Earth, and Webber only has the Earth food experience of a rural child in an unspecified-beyond-being-English-speaking country, so neither of them have ever eaten pizza. Walani is from a few decades later, so I expect she'd be familiar with it.

Alternia is like a funhouse mirror of the modern US so of course they have pizza but it's weird. It may not have cheese, at least not conventional cheese; I headcanon that they don't really do dairy ranching on Alternia because the most milkable animal is the fierce, overwhelmingly STRONG musclebeast, making it more of a delicacy for highbloods than anything

However this probably means lowbloods like Aradia and Cirava put green slime on the pizza instead of cheese. Also they call pizzas "flavor discs". I expect there's also toppings involving bugs, and yet somehow also seemingly ordinary pineapple.

(Re Walani: "Hawaiian pizza" was invented in Canada in 1962 so she hasn't necessarily had that kind.)

Thurlow is from before pizza left Italy in any substantial capacity, although before they came to the Neath they were well-travelled enough that they could maybe have been there and had some.

Purple has definitely eaten pizza since the Skeld serves enough of it to leave some lying around in the cafeteria. They like lots of pizza with lots of meat on it (or at least nutritionally complete imitation meat, whichever) and don't really care what other toppings it has.

Yochelm is the only one so far from 21st Century Earth. He likes pizza well enough. He likes it with a crispy thin crust and not too much sauce.

Well, he lives on 21st century Earth some of the time, he spends the rest of his time in the timeless void from whence he originated, it's a whole thing.

I'm sure they have λ-pizzerias in Ninuan.

There's also Detroit Agate aka Aggie, my Promethean: the Created 1e character road-tripping around North America in (2015+d10). Pizza's much tastier than garbage and still reasonably cheap and obtainable at most hours in most towns, so they're in favour of it! Their standards are incredibly low but they have a fondness for black olives.