Max Evans and OTA (Multiples Welcome)
Max wasn't exactly a party sort of guy, but the fact that there was a lot of food involved in this definitely helped. Plus, it wasn't like he had to go anywhere, since it was taking place right in his home. Or, well, their home.
He didn't know anything about cooking, and he didn't claim to know much about Mexican culture, although he spoke Spanish and had grown up in Roswell. He might have been an alien from another world, but he was still a white guy to everyone on Earth and so he didn't have to deal with the discrimination and such that Liz and her family did. The best he could do, he felt, was to accept his privilege and listen to those who actually had to deal with the bad stuff.
He was dressed casually, in blue jeans and a light blue t-shirt, and was helping Liz get all the food ready for the night.