When you are looking at the photo album, shake your 3DS. Characters and sound effects pop up out of nowhere, and the photos act like a pop-up book!
As with several other Mario games, you can jump on and attack Toad for HOURS...and he still will just smile cheerfully after.
In world S1-Castle, you can do the same thing to Luigi.
At one point in World S8-Crown, you're required to jump on a Toad's head.
The flying letter leading to World 5 shows Peach being threatened by a Goomba Tower. The one leading to World 6 shows her whacking said tower with a Parasol of Pain (complete with 1-up sound). Mario makes an approving noise and moves on, humming the theme song.
The boss battle also begins rather hilariously as a Shout-Out to Super Mario Sunshine. Bowser makes a dramatic entrance, slamming his fist down upon the floor where Mario was standing mere seconds prior. The standard boss music starts playing as Bowser and Mario stare each other down... then the music abruptly ends as the floor makes an Ominous Crack. Bowser and Mario share an Oh Crap moment together just before the floor gives way completely, dropping them both down into the boss area below.
During the boss fight itself, there's one point where Bowser abandons his usual fire-breathing tactics in favor of throwing barrels at Mario.
When you beat the first castle in World 8, it looks like you've rescued Peach... and then it turns out to be a cardboard cutout that flops over pathetically. The real humour comes in if you're watching without 3D on, as the resulting Depth Deception makes you think it really is Peach for a second.
It's even funnier if you spotted it using the binoculars earlier in the level. Even if you're playing with the 3D on, it really does fool you into thinking it's the real Peach.
Then Bowser flies away representing a certain internet meme cat...
Funny Background Event: As Mario and the Toads are flying home with Peach, Bowser tries to reach them with a Goomba Tower. They can't quite hold him...
The Propeller box and coin box powerups are pretty funny. You are just a box with legs running around!
ThisBrawl in the Family comic was made a little while before the game came out. One of the outfits designed, Tanooki Toad, is actually in the game — in the ending credits and the Special World, although it does not look exactly the same. Also, one of the other Tanooki forms appears in the final letter...