"Beware of the Blob!"
The X-Men are busy with their lives of training and teenage horseplay when the Professor senses the proximity of a nearby mutant, and sends the team to investigate. In their civilian attire, they make their way to a visiting circus, guided telepathically by Professor X, where the find freak show attraction Fred Dukes, also known as the Blob. After the show, they invite Dukes back to the mansion to join the team, but Dukes rejects them and goes back to the circus. The Blob has a better sense of his power now, and recruits the circus to his cause and brings the attack back to the school. The Professor mind-wipes the attackers, who go about their former business without memories of the X-Men.
First appearance of Fred Dukes, the Blob.
Reprinted in Marvel Super-Heroes (Vol 2) #22.