The X-Men #3

Professor X detects a new mutant and sends the X-Men to investigate. They arrive at a carnival and encounter the Blob, a very fat sideshow attraction who can bounce bullets off of his malleable hide as well as anchor himself to the earth and become immovable. The X-Men bring him back to the mansion as a potential member but the Blob spurns their invitation and returns to the carnival. Realizing that the Blob knows their secret, the X-Men lure him back to the mansion where Xavier wipes his memory.