Fitting four-mana removal into your curve is normally awkward, but paying for Pile On partially (or entirely) by tapping creatures and tokens makes it incredibly flexible in the right builds
The Tales of Middle-earth set includes four serialized cards known as Sol Rings, with three modeled after Elven, Dwarven and Human rings from the novels, and one 001/001 modeled after the legendary One Ring itself
The spell's mana value remains unchanged, no matter what the total cost to cast it was
Rakdos decks in Magic: The Gathering often have combos like this, and there are even new "one-turn-kill" strategies in Standard
Which is pretty impressive, especially when you consider what a useless, comedic character the Prince is within the story of The Princess and the Frog
Goblin Ringleader is still a leader in his own right (are you sick of these puns yet?), letting you refill your hand with two to four rabble-rousers