Who's This? That's not Jimmy Olsen on the last page of Who's Who's fourth volume.
How you could have heard of him: If you're as old as I am, you might have seen him fighting the Forgotten Villains during the original Crisis in DC Comics Presents #78, or in Secret Origins #43. If you're not, he was one of those SF heroes with a cameo in 2007's Brave and the Bold #6. That's about all Chris can get these days.
Example story: Strange Adventures #3 (1950)
So right off the bat, Chris lives up to his reputation and discovers two new planets in an uncharted system. There's a world where the people make everything from crystals, and another that's hollow with an ecosystem on the inside. Both could be interesting places to visit, but no, we're just taking readings and pictures. It's a big galaxy (/universe, the strips use these interchangeably) and you just can't set foot on every piece of floating real estate. In any case, Chris is recalled back to Earth where unknown aliens have stolen various monuments!
Chris KL-99 is an ok strip, just what you'd expect from 1950s Flash Gordon-type fare. Despite the outlandish science, it's packed with imagination, throwing away concepts other writers and artists could have made a meal of. But there's no getting away from how dated it all seems, and it's no wonder Chris wasn't seen for 35 years after Captain Comet basically took over his spot in Strange Adventures.
Who else? He's on the last page, so we're leaving volume IV behind. Volume V is next! Name your favorite obscure characters alphabetically between Chronos and Cyclotron, and I'll see what I can do to help you achieve enlightenment.