Mario Kart 7 (Community Code 44-1952-2691-6546)

[Alpha Six]

Back then lots of people didn't even know there was a Jr.,

Except that they totally did.

Except they didn't, unless they were adults that were alive in the time of DK Jr. Donkey Kong Junior (and probably the cartoons too, feel free to correct me if I'm wrong) were made in the 80s. Super Mario Kart was made in the 90s. I know that doesn't sound like much, but that's enough time for a whole nother generation of gamers.

Most people that played Super Mario Kart were kids who only played Mario and maybe the original Donkey Kong, which didn't have DK Jr. as a character. Hence, most of the kids playing SMK didn't know about Jr.'s existence.