The Warner Bros. animated series Histeria! did not have a proper Christmas episode itself, but it did have a Christmas-themed sketch, featured in the episode "The American Revolution - Part I".
The sketch in question features a comedic telling of George Washington and his troops crossing the Delaware River, set to "A Visit from St. Nicholas". Series regulars Father Time, Big Fat Baby, Loud Kiddington, World's Oldest Woman, and Miss Information also cameo in this sketch.