Remember, remember the fifth of November, Gunpowder, treason and plot.
But wait, that's not a rhyme. Still, it's all that most people know. It wasn't until I was in my twenties that I learned the next bit, thanks to Neil Gaiman's Sandman:
I see no reason why gunpowder treason, Should ever be forgot.
Who said comics never teach you anything?
The first two lines were the version I was taught as a child but, apparently, the original began "Please to remember" - a turn of phrase no longer used so hardly surprising it was altered. There are also a couple of variations of the third line.
Even more recently I discovered that there was more; it continues:
Guy Fawkes, Guy Fawkes, t’was his intent To blow up the King and Parli’ment. Three-score barrels of powder below To prove old England’s overthrow; By God’s providence he was catch’d With a dark lantern and burning match. Holler boys, Holler boys, let the bells ring. Holler boys, holler boys, God save the King!
Then the source of the tradition to place "Guys" on the bonfire:
And what should we do with him? Burn him!
Just as the UK national anthem drops the verse talking about the "Rebellious Scots to crush" so the Guy Fawkes rhyme no longer includes a section about killing the Pope by choking, burning or hanging with a rope - depending on the version.
It's ironic that we call it Guy Fawkes Night when he was just the explosives expert drafted in to set the powder and light the fuse, not the ring leader many assume him to have been. The price of being caught red handed.