The first issue of Jimmy Olsen I ever read was this one - my brother found it in a second-hand bookshop in New Zealand, a real rarity at the time because the American editions usually never got down to that part of the world (we had to be content with black-and-white Australian reprints). It was about Jimmy becoming a fifth-dimensional imp like Mr Mxyzptlk, and the only way Superman could sort it out was by getting him to say "Neslo Ymmij" - his name backwards, of course - except it didn't work, for reasons which I now can't remember. Anyway, my brother and I called Jimmy "Neslo Ymmij" for years afterwards. In fact, we still do.
You may call him Jimmy... but he'll always be Neslo to me.