LOL Well, for this particular workplace especially, "bitch-in" would be an appropriate term! But a pitch-in or carry-in or potluck is where everyone brings a different dish and there's a community meal. It happens a lot at Protestant Christian churches here Middle America, anyway. :D

The sort of thing you're calling a casserole isn't too related to what I mean, if I'm reading this recipe right. What I'm referring to usually involves eggs and/or cream of mushroom soup and is a muddle of ingredients shoved together and baked in a common dish.