Captain Marvel (the Billy Batson version) was originally published by Fawcett Comics, which DC put out of business with a lawsuit back in the 1950s. They then owned the characters, but did not start publishing the Shazam! comic, utilizing them, until 1973. This is why, in 1974, Superman fought Captain Marvel in…no, wait. He didn’t.
For reasons known only to themselves, the story in Superman 276, by Maggin, Swan and Oskner, features a character that is about as blatantly based on Captain Marvel as it would be possible to be. Willie Fawcett, whose hair is minutely shorter than Billy Batson’s, winds up traversing dimensions, ending up on our Earth.
When he says the word “thunder,” there is a lightning strike, which turns him into Captain Thunder.
He gained his powers through a strange encounter with an old man in a cave, and the word thunder evokes the names of the various gods it is an acronym of.
Captain Marvel’s series was cancelled in 1953, after the big Monster Society of Evil story arc. Willie refers to his last adventure as being against the Monster League of Evil, spanning 1953 dimensions.
The plot has the Captain Thunder identity mentally screwed up because of the dimension hopping, although Willie has his head together. Superman manages to straighten the guy out, largely by giving him a headlock. And at the end, Captain Thunder heads back to his own dimension.
It’s not a bad story at all. But it mystifies me as to why they didn’t simply use Captain Marvel, who they were currently publishing anyway.