A captain and an officer of the Science Police discusses the organization called The Legion of Super-Heroes as a macrobot experiment breaks loose in Metropolis. The captain demands that the Science Police will take care of the robot, but is then informed that the Legion already did that, and when asked "how", the officer simply responds "...they hit it, sir."
On the scene, a couple of Legionnaires are shown to have taken down macrobot. Colossal Boy detaches its head and gives it to Ultra Boy. Science Police troops appear and demands that Ultra Boy drops the head to the ground. Too late, they realize what a bad demand it was since Ultra Boy dropped the head just above them (even though Light Lass caught it with her anti-gravity field). They escaped the scene (still having the macrobot head) moments later.
On the Legion Plaza just outside the headquarters, Sun Boy asks Theena for news and updates, and then goes along with other Legionnaires to see their new member, Lyle Norg. When asked by Light Lass what his power is, Lyle "shows" them by turning completely invisible, even to Ultra Boy's superhuman vision. Lyle is dubbed "Invisible Kid" and is then welcomed into the headquarters.
But the peace wouldn't last long, not too long after, Ultra Boy alerts everyone that there is a rebellion on planet Lallor, and that every Legionnaire available would have to go to the transmatter room to get there. On Lallor, it is shown that the rebellion mostly consisted of teenagers fighting in the Legion's name. Even though Cosmic Boy, the Legion leader, is reluctant at first about supporting the rebellion, he changes his mind and tells Sun Boy, the field leader, to "go kick some @$$".
The day after, Star Boy tells Invisible Kid about why the Legion is so great. He says that the Legion isn't the core team that have costumes and code names, the Legion is every kid in the universe who wants to be one. He also tells him that the Science Police once lost their patience with the Legion and was about to destroy the headquarters, if it hadn't been for the kids there, they who formed a human shield around the Plaza. Finally, Star Boy tells Invisible Kid that they [referring to the kids at the Plaza] weren't there because of them [the core team], but rather the opposite.