Jimmy Olsen was a durable character in the Silver Age. He did not appear a lot in the Golden Age comics, although he was a regular on the Superman 1940s radio series and later on the 1950s TV show, which was why he got his own book. Olsen allowed the DC editors to touch (rather awkwardly) on teenage culture of the time, with Superman as Olsen's regular deus ex machina to get him out of the innumerable jams.
His rather nerdy and unattractive red-headed appearance appears likely to have been aimed at the Archie audience, perhaps as a bridge to bringing them into the Superman fan club. But Jimmy was an interesting character because he combined elements of both Goofus and Gallant. Capable of doing the dumbest things, he could also suddenly perform nobly and well when the situation warranted.
The first story, however, features Jimmy doing a lot of the wrong things. He turns his girlfriend, Lucy Lane, into a midget, swells Lois' head up like a balloon and turns Superman into Cluck Kent:
Of course, it's just a gag by Mr Mxyzptlk who has managed to take over Jimmy via a machine. But the lad figures out a good way to exorcise his demon:
In Jimmy Olsen and the Forty Thieves, our boy is transported back to ancient Bagdad (sic), where he had an unfortunate discovery:
Jimmy is eventually captured and sold into slavery. But there are only two possibilities for a Silver Age character sold into slavery. Either he will be sold to a hot slave-owning babe:
Or the evil villain who's also hiding out in the past. Guess which?
Luthor uses Jimmy to lure Supes back to the past, but his plot to kill the Man of Steel falls apart when Jimmy uses some nifty footwork here:
Jimmy Olsen's Secret Love begins a series of pretty embarrassing stories. The premise for the series is that both Jimmy and Lucy Lane, his girlfriend, are working undercover in disguise when they meet and fall in love. Jimmy is Magi the Magnificent, a stage magician, while Lucy is Sandra Rogers, a beautiful starlet.
Well, the negative with that humorous plot is that it makes both Jimmy and Lucy look pretty boring and unsophisticated versus the fascinating and cultured people they play in this story, as you can see from their rather pedestrian thoughts.
There was at least one more Magi and Sandra story after this.