In Action Comics #267 (June 1960), the Legion of Super-Heroes makes a re-appearance in a Supergirl adventure. Confusingly Cosmic Lad, Saturn Girl, and Lightning Lad introduce themselves as children of the original Legion members. I guess maybe DC hadn’t figured out the timey-wimey-ness of it all. Interestingly, this is retconned a few years when the story is reprinted such that these are the one-and-only Legionnaires.
Anyway the Legion pull initiation pranks on Supergirl and then bring her into the future to try out for their club. In similar fashion, something fouls up her every attempt and she doesn’t quite get in. But we do get a glimpse of three new Legion members: Colossal Boy, Chameleon Boy, and Invisible Kid, who are given a panel each to show off their powers.