Anti-Lad comes from the very distant future and travels back in time to visit the Legion of Super-Heroes and ensure that Superman became a member.
In the far, far future of the 75th Century, a young boy began a school report on the history of Superboy. Using a time scanner, he planned to peer into the past for information on Superboy's induction into the Legion of Super-Heroes. However, the device was defective, and as it peered into the past its scanning waves had somehow warped the past and altered it, so now Superboy had failed his initiation. The boy brought this to his father's attention, who explained that if something wasn't done soon their present would unravel. While his father planned to bring this to the Science Council in order to do something, the boy felt it was his responsibility to make it right. Using a few gadgets which, by his time's standards were nothing but toys but by the standards of the 30th Century they were amazing weapons, the boy traveled back in time to the 30th Century to make sure Superboy indeed joined.
The boy appeared in the Legion's HQ, calling himself Anti-Lad and asking to be judged for membership in the Legion. Anti-Lad claimed that he had the ability to reverse a person's superability on themselves, and managed to successfully defeat Colossal Boy, Lightning Lad, and Cosmic Boy, all the while acting very cocky and sure of himself. Brainiac 5 had been curious about why Anti-Lad never took off his visor, and he told him it was because his world was a thousand times brighter than Earth's, and without his visor he couldn't see.
Brainiac 5 and Cosmic Boy began discussing their mysterious new applicant and soon exposed his facade when they turned on the lights in his room and he could see fine. They learned that all his abilities were in his visor. Upon further investigation of the earth soil and kryptonite residue on his uniform from the 20th Century, Anti-Lad claimed he went back in time and sabotaged Superboy's initiation. Anti-Lad took that opportunity to depart the Legion back to his time, using his visor to erase the Legionnaires' memories of his time there, but with the post-hypnotic suggestion that they should give Superboy another chance. The timeline had been corrected and Superboy did indeed become a member.
No one remembered Anti-Lad's time in the Legion, but the only thing left behind was a picture of Anti-Lad with Saturn Girl, Lightning Lad, and Cosmic Boy. This led the other Legionnaires to wonder, "Who was Anti-Lad?"