No-Legs is an NPC found in the area of the Nightmare known as Inside. He has several lines of text, talking mainly about his lack of legs, but he also refers to 'Mr. Earth'. Who Mr. Earth is is currently unknown.
No-Legs is also a vendor. He will sell things added in the Ratboy's Nightmare update, also obtainable from the Green Golem, for example Salamander Eggs and Nightmare Boots.
To get to No-Legs, players must complete the items-in-boxes puzzle in the Mansion, then press the button on the hearth Inside (bottom floor). This will then unlock a portal door in a room leading off the corridor preceding the Fish Hall. Taking the portal will teleport you to the attic of Inside, visible from the top floor of the Inside region. There is a ladder leading up to the attic, but it has been blocked off by boards at the top. The portal door is the only way in.