The Nick at Nite Holiday Special was a holiday special that aired on Nick at Nite on November 28, 2003. It starred Martin Mull, Jackee Harry, Joyce DeWitt, John Schneider, and French Stewart. Clay Aiken, Ted Danson, Al Roker, and Raven Symone, among others, also made cameo appearances.
No footage for this special exists on Youtube or any other video site, except for a musical number between Clay Aiken and Bing Crosby: https://www.youtube.com/watch?v=_QHlaTZMmQY
There is also a website that shows some pictures of the special, specifically Clay Aiken's scenes: http://claynewsnetwork.com/tag/the-nick-at-nite-holiday-special/
There are also various photos of the special on getty images: http://www.gettyimages.com/detail/news-photo/raven-during-nick-at-nite-celebrates-the-holiday-season-news-photo/175148017