It definitely isn't that. I just installed and played CTGP today, which got me thinking about the Mario Kart Wii mod I'd played years ago.
It had a lot of dumb custom stuff. Dubstep music, coca-cola tracks, "broken cup" cup, and I specifically remember a pic of Mario smoking weed on the initial Wii strap screen. I can link to videos of it and the original reddit post the creator made, just not on this site. (of course the download links are dead, or I wouldn't be writing this)
If it was made recently then I would assume the mod would only contain its own files, judging by the mario kart wii mods I've found. But it was made 9 years ago according to the reddit post, and I don't know how mario kart wii mods were distributed back then.