The guild letter for the Izzet is also chuckle-worthy.
Welcome to the Izzet League, achievers of the impossible! Your work has led you to the guild that tries the untried, challenges the status quo, and defies such tedious concepts as "good enough" and "laboratory safety." Our mission is the venture unflinchingly into the unknown, with no concerns for the risks. Others may fear the volatility of our endeavors, but isn't ignorance the greatest danger of all? We understand that knowledge cannot be gained without passion, and that an explosion is the result.
In "The Secretist, Part 2", by Doug Beyer, Jace gets into a fight with Ruric-Thar. Unable to defeat a giant, two-headed,magic-resistant ogre with his usual arsenal of tricks and illusions, Jace throws the book out of the window and bites them in the kneepits. They are amused enough by this to concede and give him what he wants.
Cards are not popular just for their effects, brokenness or artwork. Many cards find their ways into players' hearts because the Flavor Text accompanying the card ties everything together and is often hilarious.
During the launch party for Unglued (the joke set that makes fun of Magic itself), Mark Rosewater took the role of a judge...while wearing a chicken suit. He wore a donkey suit for the release of the sequel set, Unhinged. On a related note, Mark also made a list of his favorite funny quotes from the players at the Unglued launch party, found Here (at the end).
Anytime you and your friends play a game of Magic where Unglued or Unhinged is included. Anytime. Just an example:
(on turn 3) Friend 1:(stoic) For 3 mana, Farewell to Arms. Right hand. Go. Friend 2:(manages to go through his turn with his right hand behind his back) Go. Friend 1:(still stoic) For 3 mana, Farewell to Arms. Left hand. (smiles) Play with your feet, motherfucker.