I am using Ubuntu Linux 9.04 Jaunty... When I was able to get it in it didn't show up in my App Box but actually showed up in my Applications already it was just without a thumbnail... What OS are you running and what version of Boxee and I'll attempt to help you get it up and somewhat running... Just to let you know all Cartoon Network vids are cut in two by commercials and the python script doesn't quite get it right (no offense) so most of the time you get to watch half of the show and it either A. starts over or B. goes back to the selection screen and continues the second part... LOL... Lemme know...
EDIT: Ok I know where your problem lies... What version of windows are you running? That will help me more than anything as the problem you are experiencing is because you are editing the wrong file... The one you want to edit is under your "home" directory... IE
In Vista the file you want would be C:\Users\<username>\AppData\ROAMING\BOXEE\userdata \profiles\<user>\sources.xml
Take into account to be able to find it you will probably need to turn on Show Hidden Files, you can do that by following this link
Show Hidden Files Tutorial
Also you will want to put the cartoon directory in C:\Users\<username>\AppData\ROAMING\BOXEE\userdata \plugins
I'm not 100% familiar with where it would be in Windows XP but I'm sure I can find it... Just let me know...