Super Mario 3D Land runs on the same engine as Mario Galaxy but it supported assets & features from Mario Sunshine. This means that the level of hacks/level mods that graced the Nintendo Wii Galaxy games could come to the 3DS when the time was right.
Apparently, the time is 2016 as two videos released showing the Nintendo hacking community bringing old Mario levels into 3D Land. The above video is of Mario Sunshine’s Bianco Hills while the blow video is the iconic 1-1 stage from the original Super Mario Brothers.

Its nice to see fans show there love & support toward gaming IP with these fan hacks, as it shows how flexible and adaptive the 3D Land engine is with new levels.