Yes, that is a GIANT picture of John Lennon. Now that we have addressed it, let us move on.
I'd love to know what the most covered song of all time is. I'll have to get my hands on some stats and get back to you. In the mean time, I've got to believe that John Lennon's "Imagine" is up there, top ten at least. When your song is covered by everyone from Gregorian monks to the cast of Glee, you know it's stood the test of time. I found ten, count 'em ten, different versions of the song for you. Fair warning, some of these are pretty bad. Blues Traveler is particularly painful (big surprise there). Enjoy!