At one point or another, these five men were principals in this well known multi-media entertainment venture: Leonard; Arthur; Julius; Milton; Herbert. (Note: no tricks here – those are real names, not the names of characters they portrayed, or some-such.)

As always, you are on your honor to refrain from using search engines (that takes all the sport out of it. 🙂 )

Update: Congratz to reader Andrew V. (see comments)