Contributed by Funland47
If enough time passes at the end of World 4-4 and at the beginning of World 8-4, a ghost appears. Looking at it for long enough will cause it to open its mouth (sort of a silent scream) and then disappear.
Contributed by pyropupet
Super Mario 3D Land is the first platformer game since Super Mario World where Mario cannot perform a triple jump. Luigi however, can.
Contributed by WiiWizard
World 5-2 is designed in a Legend of Zelda format, using a top-down view, lots of rooms, and no stompable enemies. Also, if you light all of the torches in a certain room using a Fire Flower, a secret door opens and a Zelda sound effect is heard. The level was designed in honor of LoZ's 25th anniversary, hinted at by the level number: "5-2" is "25" backwards.
Contributed by DidYouKnowGaming
In World 1-3, if you look up with the binoculars and wait, a UFO will fly by.