I know this board isn't super active, but I have not many places to discuss a little about "references to other games" sort short of enacting a proposal (and then possibly getting comments that have perspective I never thought of, so I don't want to go to proposal route yet). I've looked at Mario Tennis Aces and I noticed a lot of its references were basically just "stock art that just so happened to first appear in x game is in Mario Tennis Aces and so it's a reference to x game". Or, a voice effect that has been reused from another game even though they might as well be stock. I feel we should narrow that down more. Of course there's sometimes a little debate on what's "stock" or not, but I don't think it's necessarily a reference to Mario Kart if Mario says "whoohoo" in Mario Tennis in the same way as he did in Mario Kart.