Surprised no one else has started a thread on this (Fry, you still updating?), but I've found a few things. I have photos of a few on Miiverse, but I need to remember my password to get to them. XD Anyway!
Urchin Underpass has two cameos: an Octorock sprite from the original NES Legend of Zelda and a Blooper sprite from the original NES Super Mario Bros. They can be found on the leftmost path on your way from the spawn point to the central area.
Bluefin Depot has a piece of graph paper with an Octorock from Zelda II: Adventure of Link on one side of the stage. It's on the backside of one of the white slabs up on the third tier from your spawn point.
There's a few cameos in single player's Scroll unlockables as well, but I don't exactly remember them at the moment. I'll look in there and update this when I get a chance.
Flounder Heights has some more sprite cameos: The Blooper sprite from Super Mario Bros. 3 makes an appearance, as well as the Gunion enemy from Super Mario Land! Nice to see a nod to that one. Also, there are Triforce-esque hopscotch games on the floor in a few areas.
I've got screens of these on my Miiverse, but I need to remember my password. XD
Similar to the N-ZAP '85, the N-ZAP '89 is based on the American version of the NES Zapper, which was made orange in May of 1989 after the Federal Energy Management Improvement Act of 1988 was passed, requiring toy guns to look drastically different from real guns. This is referenced in Sheldon's description of the weapon, stating the design had to be changed due to "legal reasons".
The box art layout of the of the mini games seems to be reference to the style used by some Famicom game box art, where the game name (on left) and publisher (on right) were placed above a (cartoony) scene to represent the game.
As you can see above there is a Mario amiibo on a white Wii U Gamepad (like on most other amiibo back covers).
The box seems heavily based on the Inkling Girl version. The layout of inksplatters on the front of the box seems to be using most of the colour placement/splatter layout of the Inkling Girl amiibo front box art and back of the box displays the girl and it's unlockables.
I spent way too long making this post.
Last Edit: Aug 26, 2015 18:07:41 GMT -5 by Da Robot