These fellas are hidden in very hard-to-reach areas. They fly around Chase just like in Mario 64, complete with the familiar 'invincibility' fanfare. To get this particular one, you'll need to jump down onto the grassy peninsular above Paradise Sands (by the observatory) and leap across using a Super Chicken Glide. See - we said it was useful!
Crescent Park has a little waterside promenade and on it you'll find this fishing rod. Win the simple minigame and, unlike other fishing rods in the city, you'll be rewarded with a Cheep Cheep. He slips back in to the water after leaving a blue stud on the floor. Must've been scared.
Red bricks unlock a wealth of cool content (as you'd expect from a LEGO game) so imagine our surprise when we found Mario's hat. We're pretty sure it's on Apollo Island... but we're not 100% sure. Sorry, truth is we've seen so much LEGO recently we feel a bit funny.
Once you've got the Smelly Overalls outfit from the farm, head around the back of the dojo and you'll find a familiar green pipe. Water it with your watering can and a Piranha Plant emerges before proceeding to spit fire at you. We've tried everything to kill it but to no avail. You can, however, use his fire to burn the nearby spider's web away with quick dodging and retrieve a bonus.
After you finish the game you'll be able to find and open a Mario-style warp pipe to reach Lady Liberty Island, which is off-limits to the public for most of the game. We're not supposed to tell you exactly where said warp pipe is, but we will say Uptown would be a good place to start and you will have been a few yards from it already during the game.
What can you find?
As we say, we're not quite at 100% yet. So there could still be more Nintendo cameos to discover. Let us know in the comments if you find any good ones and we'll update the article if we find any more.
And if you're looking for more, check out Why you might never actually start the story in LEGO City Undercover and our LEGO City Undercover review.