It's at <ftp://24.0.172.162/pub/RM/holynight.rm>. <ftp://24.0.172.162/pub/> contains lots of other South Park cartoons, in RealVideo and Quicktime.
Here is a list of the current contents of my FTP site.
/pub/RM/holynight.rm -- The South Park music video. Cartman sings and Kyle helps him remember the words. DL from <ftp://24.0.172.162/pub/RM/holynight.rm> /pub/RM/so-leno.rm -- South Park on Jay Leno. RealVideo format. Very good quality! DL from <ftp://24.0.172.162/pub/RM/so-leno.rm> /pub/MOV/soxmas.mov -- The Christmas episode, with Jesus fighting Santa Claus. QuickTime format. Pretty good quality. DL from <ftp://24.0.172.162/pub/MOV/soxmas.mov> /pub/RM/soxmas.rm -- Same thing, but a lot smaller. Decent quality. DL from <ftp://24.0.172.162/pub/RM/soxmas.rm> /pub/RM/so-frosty.rm -- Another South Park cartoon, one featuring Frosty. RealVideo format. Very good quality! DL from <ftp://24.0.172.162/pub/RM/so-frosty.rm> /pub/MOV/so-frosty.mov -- Same thing, but QuickTime format, a lot bigger, and worse quality. Get this one only if you can't play RealVideo. DL from <ftp://24.0.172.162/pub/MOV/so-frosty.mov> /pub/MOV/so-frosty.mov.gz -- The QuickTime version, compressed. DL from <ftp://24.0.172.162/pub/MOV/so-frosty.mov.gz>
<http://24.0.172.162/pub/> mirrors this directory.