I already know this one
Can you tell me VB land one pls
Viewing post in NSMB Mario Vs Luigi - KKT's Gooffy little Mod (V.1.1.0) comments
In VB land, if u go to the right and see about 3 pipes, go to the middle and crouch, then jump and after u jump there should be a mini pipe above, go inside it and after u enter it, keep jumping upwards and you'll find the challenge.
(PS: u need Luigi with abilities on for this, and u need mini mushroom too)