"iPod Nano Catches Man's Pants on Fire"

What did the poet want to say with this caption? iPod was chasing the pants, and Fire was the place where it caught them?

Or it's a new PC expression. It's not that "guy A set the barn ablaze", it's "Guy A Caught the Barn on Fire".

Or maybe Man's Pants on Fire is just another weird toponym, like Stratford on Avon.