My Chief Research Assistant (Mom) found me a bunch of pictures of ugly Christmas sweaters on the internet, and I have carefully studied these photos to find out what makes a sweater properly ugly.
The first thing I noticed was that these sweaters have really bright colors. Usually, these colors are red and green, but sometimes they're a different color, such as pink.
Religious sweaters are good, like for example, with the Baby Jesus on them.
Here's a clever sweater that looks like a Christmas tree. It even has tinsel and ornaments!
Rudolf looks good on a sweater, especially if you can get a nice 3D effect.
But I think the very best kind of Christmas sweater is one with a famous person on it, because who wouldn't want to share their holiday with Elvis or with Abe?