Elvis Masada's Place is an area that can be accessed from Mushroom World by means of the portal to the north of the main entrance.
Features
The most notable feature in this area is, of course, Elvis Masada himself. To find him, simply go through the door on the left from the portal entrance. Interacting with him normally will prompt him to play a pleasant melody on the piano. If you equip the Trombone effect and interact with him, an event will occur where Urotsuki and Elvis play a duet. If you equip the Chainsaw effect and interact with him, he'll play a collection of random notes out of fright.
If you take the door at the top of the room with the portal, you'll go into an image gallery of sorts, which eventually leads to a room with a large tank of water with a giant humanoid figure suspended in it, which leads to a dead end in another world. If you take the door on the left wall in Elvis's room, you'll end up in another room with four chairs. Going down and then right from here will take you to a room with a portal to the Sky Kingdom. Going left will take you to a heart-themed world distinct from Heart World. Going up will take you to a room with a mirror and a ghost. If you use the Chainsaw effect on the mirror, there is a chance that the mirror will shatter and that Urotsuki will be transported to another room. If you break the mirror in that room, she'll be teleported back to the room with the ghost, but the ghost will be absent.
Connections
Metal Pipe World (?)
Other heart world (?)