In the early days of Magic, judges used to carry around a loose-leaf binder that had color copies of every Magic card in existence. This book would be used as a reference to settle rules disputes, as in those days the cards always overrode the rules. (These days the Oracle is the primary source for card text.)

Included in one of the printings of the God Book were two "joke" cards: Painful Hedgehog and Urza's Lawn Ornament. These cards did not exist in real life, and were placed there purely to mess with the minds of the judges.

Painful Hedgehog had a picture of "Sonic" from the Sega game systems. This card was a 1/1 green creature with first strike. Urza's Lawn Ornament is a 4 mana artifact that probably had a picture of the ubiquitous pink flamingo, with an ability to tap to destroy a target land.

InQuest #28 revealed information about these cards in their article "101 Magic Facts":

If any old-school judges out there still have this book, please scan me a picture of these cards! Thanks.