An Upwarp is a phenomena where Mario's vertical position is suddenly updated so that he appears to warp upward. There are a few types of known upwarps.
Tick Tick Clock Upwarp
Hangable Ceiling Upwarp
The hangable ceiling upwarp is an upwarp caused when Mario single jumps or double jumps into a ceiling at its edge, while under a higher hangable ceiling. This upwarps him to the higher ceiling, and he begins hanging on it.
Water Surface Upwarp
Whenever Mario enters water, he is always warped to the surface of the water before he can swim. The upwarp effect is observeable in courses such as WF, TTM, and THI small island.
However, a ceiling hitbox can immediately push him back down so that he never remains at the surface of the water. This is observable in WDW in downtown when the water level is overflowed.