"Mexican casserole" is a surprisingly popular "white people TexMex" dish. It is made by taking ingredients for a TexMex enchilada dinner (enchiladas with rice and beans) and then just throwing it all in a casserole dish. The mildest available enchilada sauce is used, probably only a couple tablespoons for a 13x9 pan. If you're unlucky, your host used flour tortillas instead of corn and they all got gluey in the oven.
The strangest I've had thankfully hasn't caught on: a tamale casserole meal donated by a white lady to a largely Hispanic student group. It was made by buying enough tamales to fill the foil pans, unwrapping them all, and layering them in with sprinkles of unseasoned cooked ground beef and handfuls of shredded cheese, and heating until the cheese melted. We were pretty confused and just picked out the tamales.