I've looked around but no one seems to have mentioned this interesting anomaly from EC's Two Fisted Tales #39, dated October 1954. This was the fourth issue of "The New" TFT, edited by John Severin and written by his friend Colin Dawkins.
Severin drew a couple of early issues all by himself, though he soon took on other artists to spread the work load. Issue #39 was one of the all-Severin issues...or at least, Severin signed all the stories. But check out this Cold War wish-fulfillment story, "The Secret"--signed by Severin, but clearly pencilled by Gene Colan!
Colan had drawn a couple of war stories for Harvey Kurtzman, and I recall reading somewhere that Kurtzman didn't particularly like them. We can see from this story that Colan already had his drawing down solid. I think it took him a few more years to work out his inking style. Though Severin laid his personal style on heavily, he kept much of Colan's spirit.
For the evidence-hungry: Look at the character design of "Nick" and his posing and expressions on page 1. Panels 4 and 6 of page 2 are pure Colan, as is the group on page 3 panel 4. The real clincher is panel 4 of page 4. Colan is noted for re-using photo reference, and a decade and a half later he used this shot several times in comics like Iron Man. And on page 6, Genial Gene shines through again in the shots of Nick in panels 3, 4, and 7.
I wonder how this team-up came to be.
(I apologize sincerely for the messy edges. I scanned these from Russ Cochran's hardbound collection, and this is the best I could get without breaking the binding.)