Sonic the Hedgehog
Outlaw chili dogs.
Dye his fur black.
Steal his shoes.
Call him a rodent.
Tell him all his friends switched to Eggman's side.
Dress like him and stalk him.
Tell him Eggman switched to the good side.
Openly express your Mario fandom over and over.
Mention Princess Elise.
Give him Shadow's shoes.
Pepper spray him because he stole your wallet.
Hand him this list.
Just tell him that he grinds your gears.
Establish a Tails awareness day.
Openly express your Shadow fandom over and over.
Mention that moment in Sonic 06.
Get in his way when he's going for his morning jog or something...
Sing Beyoncé when he's around.
Remind him that he isn't even the fastest in his own game.
Make him participate in a race and rig it so that he finishes last.
Take him to an Eggcon. (Eggman convention)
Play T-T-FAF-A-FAF the next time he battles Eggman.
Hold a secret wedding with Amy and a Sonic poser.
Beat him in a footrace by any means necessary.
Ask him whether Elise kissing an animal or a corpse is weirder.
Mention how Mario is better at kart racing and tennis and golf and baseball...
Randomly yell, "I'm not a rat, I'm a PINGAS!"
Mention Sonic 06.
Give him a copy of Sonic 06.