Bowser Jr.'s Fiery Flotilla 1
From Lumapedia
Advanced
0:00 - Do not skip the Intro Cutscenes for RTA simulation.
0:13 - Aim to get a Frame Perfect Jump here as it will allow you to make a faster cycle on the Thwomp, as seen here
0:51 - DO NOT SKIP THIS CUTSCENE (Gobblegut's position relative to the camera can change if you do)
1:11 - For the third hit, Gobblegut's position can vary quite a bit. You have a decent window to react to this and angle your backflip in the right direction.
1:23 - Use the Coin embedded into the ground as a visual cue for when to turn around.