2D Skip Skip
2D Skip Skip, often abbreviated as 2DSS, is an extremely difficult trick in the Bowser escape section in the Moon Kingdom that involves scaling the outside of the 2D section by landing on very small pieces of collision to save approximately 7 to 8 seconds. The name of the trick is a pun, because the trick bypasses 2D Skip, and the abbreviation 2DSS pays homage to the trick's similarities to Dino Skip Skip, or DSS. The skip was found by MiiWii.
Explanation
The geometry of the 2D wall is made up of multiple individual sections that normally fall one at a time as the player climbs to the top of the 2D section from the inside. For some reason, the way Bowser interacts with the collision allows him to stand on the seams between these sections for an extremely brief moment. This allows the player to scale the tops of the sections one-by-one to reach the top of the 2D area without entering it, saving precious time.
Interestingly, performing 2DSS is the only known way to skip the 2D section and the associated Honeylune Ridge: Collapse (8-Bit) music track. If the skip is performed, the track will not show up in the music list that appears after beating the game.
Speedrun usage
Because nearly all speedruns of Super Mario Odyssey involve beating the game and completing the Bowser escape section, 2D Skip Skip theoretically saves time in almost all categories. A notable exception to this is categories that involve acquiring all music tracks, such as 100% and All Music, since 2D Skip Skip bypasses the music associated with the 2D section.