Superman #127 (the February 1959 issue) included a story titled "When There Was No Clark Kent." It had a typical plot for the era -- While working on a story for the Daily Planet, Clark is apparently killed in a factory explosion. Superman tries to carry on without a secret identity, but the lack of privacy and the constant requests for his assistance convince him that he needs his second life as Clark. So, he concocts an elaborate (but plausible) story of how Clark survived the accident, and the status is quo once more.
But the last panel of the story is peculiar. At the very end, in response to nothing at all, Clark thinks "He sure will!" Who is this mysterious "he," and what is it exactly that "he" will do? Is this a cliffhanger ending, suggesting a possible sequel?
I first read this story in 1967, when it was reprinted in Superman #197. Clark's thought balloon was missing from that reprint, carefully removed by an observant editor. In the eight years that had passed since the story was first published, did "he" complete whatever enigmatic mission that Clark had promised? Or was this part of a conspiracy to cover up "his" activities? If so, it failed, because the story was reprinted a second time in 2005, with Clark again assuring us that "He sure will!"
If Superman himself tells me that "he sure will," I have to believe it. Maybe "he" already did. If we only knew who, what, and when, we could be prepared. I don't know about you, but I'm going to keep looking over my shoulder.