I'd say either Rocko or Arnold's Christmas episode. I also still watch Danny's Christmas episode every year.

@JeremyCreek

Yeah, well it ain't bad but how most of the Danny Phantom Chrismtas special is played out is one of the reasons I'm still routing that they give Danny Phantom a shot at the spotlight again for a revival series continuation to get a new but better Christmas special that involves say not only Danny giving Danielle her special first Christmas, few episodes after she got adopted into his family, as she was originally planned to be so, had the continued, but also have his parents start learning on becoming better for him and Jazz, through both him and Danielle while also start changing their hostile perspective on ghosts through both of them too.