I was remembering this game and was curious about it's origins too. I'm a month short of 23 and I remember playing this game on bus rides to/from school way back in elementary school. I don't remember exactly how it went, but the version went something like this:

While lightly pounding on the person's shoulders from behind: Concentration, idiodiation,
Crack an egg on your head and feel the yolk run down your back (bump person's head with your fist and trail your fingers run down their back) x2
Concentrate, Concentrate (pounding shoulders)
Squeeze an orange on your head and let the juice run down your back (trail fingers down head/back)x2
Concentrate, Concentrate (pounding shoulders)
Stab a knife in your back and let the blood run down your back (Pound a fist on their back and trail fingers)x2
Concentrate, Concentrate
Spiders crawling up your back, Spiders crawling down your back (trail fingers up and down)x2
Cool breeze (blow on person's neck)
Tight Squeeze (Squeeze person's shoulders)
Now you've got the chills! (or shiverees... I remember that too).

We didn't make up any variations that I recall, and I'm not sure if this is exactly correct, but this is how I remember it.