This is a really cool fanfic you have here. Sorry if I lead you on about that Fan Art thread. Was just trying to get other's opinions about why Mario and Sonic are always included in fan art.
Author's response
Ha, no worries. I was just confused as all hell when that title wasn't worded more... appropriately. Also, I think you're exaggerating the situation a bit. Mario and Sonic aren't ALWAYS included in fanart. In fact, I wasn't even aware there was an issue like this until you posted about it. Go do some browsing around deviantART, especially in group galleries which are devoted to the shows you like. You're bound to find stuff there to suit your tastes without the offending characters present. :)
And stay away from Tumblr... horrible, horrible place.