Firing is a hard process. We're here to help.
Send him a glamour shot of Bobby Petrino. He'll know what it means.
Hand him a fortune cookie in Chinese. When he asks what it means, say "I don't know, but you're fired."
Turn him into a dog. Have him adopted by a loving family who has two other pets: a scrappy mutt, and a saucy cat. The family will go on a vacation across the country, but the sitter won't show up! Then the three will convene. In universal petspeak, they decide to embark on an arduous, hazardous, and thrilling voyage. Then a semi hits them all when they cross the street, and the movie ends.
Shave "You're fired" backwards into his chest hair while he's asleep.
If this doesn't work, shave it into his wife's personal hair. (NOTE: requires high degree of cooperation from wife.)
Invite him to play a game of Call of Duty online and make your clan tag [FYRED]
Strike up a conversation about your favorite cartoon characters, and when he asks you who yours is, say "FIRED Flintstone." THEN LAUGH AND GIVE HIM FINGAGUNZ.
Make a list of your favorite bands, like Arcade FIRED and Earth, Wind, and FIRED.
Take him to the mall. Go to Wired and Fired. Point at the second half of the sign and say, "That's you."
Set your pant cuff on fire. Run down the hall and past your coach's office. Yell "Fired! Fired!" Your coach will tackle you, and put out the fire, and save your life. Then, you should say, "Thanks, but I was saying 'fired,' and was referring to you. The other thing was purely coincidental.'"
Bake him a cake that tells him he's fired. Not because you care, or because it's any easier, but because he'll probably cry and eat it at the same time, and that's never not funny.
Fire him, and then say "Just kidding! I'm promoting you!" When he smiles and asks, "What's the promotion?", say "You're the new FIRED chief!" Then slap a red fireman's hat on him and circle him while making a "WOOOOO" siren noise and squirting him with a water pistol.