Explanation: Pretty simple Out of Bounds, you walk around the room and go to the hammer. You can use this to also get to Grobot early. For Grobot early, just walk down as shown here

IMPORTANT: If you use this for Grobot early, you will need the Bros. Attacks in order to beat later bosses fast. Get the 3D Red Shell before performing the Grobot early!

Time saved: about 5 minutes (Grobot early should save about 8 minutes if you remove the time needed to get 3D Red Shell)