It's the yearly tryouts for Legion Membership, and five applicants don't do so well. Porcupine Pete can't control his powers, Chlorophyll Kid can make plants grow (but can't control or shrink them), Infectious Lass makes people sick, Color Kid can only make things change color, and Stone Boy... turns into an immobile stone statue.
Two new members are inducted into the Legion, Matter-Eater Lad and Star Boy. Bouncing Boy gives an encouraging speech to the five rejects before taking off with the rest of the Legion on a mission. The five rejects resolve to fight crime on their own, and patrol Metropolis... with no significant success.
Meanwhile in orbit, the Legion find themselves fighting a creature that is sucking away the Earth's ionosphere. The newest members easily defeat it... but more arrive. The Legoin are forced to call in reinforcements as more and more of the creatures swarm the atmosphere.
Back on Earth, the rejects come across a villain, Starfinger, who uses two gloves each one containing five deadly finger-powers. He readily defeats the rejects and leaves with his loot, using a group of small furry creatures to carry the goods that he generates from one of his deadly fingers, creatures that tend to drift off up into the sky.
The rejects follow Starfinger back to his headquarters and take him on. They are actually able to fight him to a standstill, but Stone Boy is covered in the furry creatures and pulled up into the atmosphere.
Above the Earth, Brainiac 5 has determined that the only way to stop the giant creatures is to use an energy device that has a significant chance of igniting the Earth's atmosphere. Stone Boy arrives carried by the creatures, which mutate into the ionosphere-eating beasts. He quickly realizes what's going on, turns to stone, and plummets back to Earth, landing on Starfinger as he is preparing to defeat the other rejects.
The rejects quickly realize what's going on and manage to get up into the atmosphere with the aid of Porcupine Pete's mother, taking the captive Starfinger with them. Bouncing Boy and Lightning Lad believe their story and Brainiac 5 converts Starfinger's weapon glove into a device to send the mutated furries away.
Back on Earth, the Legion congratulate the rejects on their success. They suggest the members audition for the tryouts next year, but the rejects success they might remain as their own group, as a "Legion of Substitute Heroes" to provide backup when the Legion is busy elsewhere.
The Legion of Substitute Heroes
The super-powered individuals who would become the Legion of Substitute Heroes first appeared in Adventure Comics #306. Each member was a rejected applicant for the Legion, dismissed due to some perceived weakness. Disappointed, one of the applicants, Polar Boy, formed the other four into a group to act as a "substitute" Legion. They served secretly for a while, but eventually the Legion found out about them and recognized their services. Since then the Substitute Heroes have served nobly, both when the Legion is unavailable and when additional manpower is needed.
Although the Substitute's membership has changed over the years, the core members are considered: Polar Boy (Brek Bannin, native ability to project cold), Fire Lad (Stag Mavlen, ability to breathe fire), Night Girl (Lydda Jath, super-strength and invulnerability in total darkness), Chlorphyll Kid (Ral Benem, ability to accelerate plant growth), Stone Boy (Dag Wentim, native ability to go into a petrified form of suspended animation), and Color Kid (Ulu Vakk, ability to cause anything to change colors).
Starfinger originally appeared in Adventure Comics #336 (Sep. 1965), and was a masked figure with ten weapons mounted in each finger of his two gloves. It was revealed that he was actually Lightning Lad, hypnotically controlled by Dr. Hans Lanscom. Lanscom was brought to justice and briefly tried a criminal career on his own. Lanscom was later killed by another man who took the role of Starfinger. Later Molock Hanscom took on the role, his appearance resembling the one in the animated series. He was able to generate two super-powered women, Starlight and Starbright, from his super-powered fingers.