I thought that the origin of Captain Marvel (as told in Whiz Comics #2, 1940) hadn't been tampered with or tweaked until 1973 and after with the multiple reboots and reintroductions of Cap. That thought was dashed when I watched all 12 episodes of the Adventures of Captain Marvel. Holy Moley - they tampered with Cap's origin in episode 1 and in episode 12! I won't go into all the details of the plot, etc., but below are the details of how Cap's origin was changed.
In episode 1, we find Billy Batson with the Malcolm Archaeological Expedition in Siam trying to discover the lost Scorpion Dynasty. It is here that Billy meets Shazam. Shazam tells Billy that it is his duty to see that the curse of the Scorpion doesn't fall on innocent people. He, as Captain Marvel, is to protect the golden scorpion from falling into evil hands. Shazam declares, "It is the duty of Captain Marvel to protect the innocent from its evil use. You must never call upon this power except in the service of right. To do so would bring the Scorpion's curse upon your own head." Billy says, "Shazam!" and turns into Captain Marvel and Shazam disappears.
Episode 12 is the final episode in the serial. Here we have Captain Marvel destroying the golden scorpion by throwing it into a volcano. Once it has been destroyed, you hear a deep voice say, "Shazam!" and Captain Marvel turns back into Billy Batson - never to become Captain Marvel again! Captain Marvel could only be around while the golden scorpion existed and now that it has been destroyed, there is no need for Cap!
I was simply amazed that they had altered the origin of Captain Marvel so soon after he was introduced in Whiz Comics #2! I wonder if there was any outcry from fans because of this? As a fan of the original Captain Marvel I'm often disappointed at the various iterations that have been printed about Cap's origin post 1973. But now I see that it isn't a new thing - it's been tweaked from the very beginning!
For your viewing pleasure, here's episode 1 of the Adventures of Captain Marvel.