As superheroes continued to grow in popularity with young comic book readers, creators found a way to strengthen their appeal by adding youthful sidekicks. For Captain Marvel it was Freddy Freeman, aka Captain Marvel Jr. The boy turned superhero was created by Ed Herron and Mac Raboy, appearing for the first time in Whiz Comics #25 (December 1941).

Freddy and his grandfather Jacob were on a fishing trip when it was interrupted by a fight between Captain Marvel and Captain Nazi. Captain Marvel slugged his nemesis with an epic punch that sent him sailing into the lake. Trying to help, the Freemans pulled the unconscious man into the boat so he wouldn’t drown, but once the villain was revived, he threw both grandfather and grandson into the lake. Jacob died, but Captain Marvel was able to save Freddy and rushed him to a nearby hospital.

Medical professionals projected that Freddy wouldn’t last the night, so Captain Marvel took the boy to Shazam’s secret throne room to see if the Wizard could save him. The Wizard declared that he could save Freddy, but wouldn’t be able to reverse damage that had been done to him. This is achieved when the Wizard passes some of his powers on to Freddy, which in addition to saving his life, turns the boy into the superpowered Captain Marvel Jr.

When Freddy awakens, he sees Captain Marvel and by saying his name turns into Captain Marvel Jr. He gains the Shazam powers of wisdom, superstrength, stamina, power, courage, and speed, as well as the ability to fly, accelerated healing, and some electro-kinesis and electro-blasts.

Unlike Billy Batson, when Freddy changes, he stays in his teenage body, though with the same powers as Captain Marvel and becomes his crimefighting partner. Billy warns Freddy that he cannot stay in his Captain Marvel Jr. form because he must allow his human form to heal. When he changed back into his regular body, Freddy discovered that his left leg had been permanently injured in the accident and he must now use a crutch to walk.

As a superhero, Captain Marvel Jr. fought against the Axis powers during the World War II era of comics. He was able to remain inconspicuous to the public and protect his identity as Freddy by wearing shabby clothes and living in rundown accommodations. Despite having nearly limitless powers as a superhero, Freddy always returned to his human body with its injured leg to heal and preserve his powers so that he could continue helping others as a superhero.

Throughout the Golden Age, Freddy would engage in adventures alongside Captain Marvel, the Shazam family, and in his own self-titled Captain Marvel Jr. comic which lasted for 9 years and 119 issues.