Ice Corner Clip
Ice Corner Clip, often abbreviated as ICC, is a corner clip in the Icicle Cavern room in Snow Kingdom that allows the Ice-Dodging Goomba Stack moon to be collected without capturing the Goombas and activating the button. The clip was discovered by Xdxboxjaja[1] and is speculated to save around six to eight seconds in the Any% run, depending on the route used.
Explanation
Because the wall used for the corner clip is not adjacent to any ground, the clip must be performed in midair, and failing the trick will result in a death. Because Ice Corner Clip is so precise, this makes it a very risky trick to attempt in speedruns. Some players have attempted to devise a setup for the trick using first-person camera mode, including MadeForMario. Video
Normally, after performing Ice Corner Clip, Mario will end up stuck inside the alcove where the moon is, since the wall covering it has collision on both sides. In this case, the only way out aside from reloading the save file is to warp to a Checkpoint Flag on the map screen. This can be worked into the speedrun route if the Icicle Cavern room is entered last, and the Story Moon in the room is collected first before performing Ice Corner Clip. Instead of entering the Crazy Cap shop last like in the standard Any% route with Snow Dram, the shop moon is obtained earlier in the route so that Icicle Cavern is the last room to be entered.
However, it is also possible to stay halfway out of bounds while collecting the moon after the clip, so that Mario does not become stuck and can continue the route as normal. This eliminates the need for a reroute of the kingdom and is speculated to be faster than the altered route, although it makes the trick significantly more difficult since the moon must be grabbed from a precise position. Video