Wear socks outside of shoes?
Pants backwards?
Merrily skip everywhere you go?
Narrate your life?
Speak at varying speeds?
Buy a tape measurer, and measure tons of inanimate objects (tables, doorways, chairs, ketchup bottles, et cetera), and keep a record of them?
Wear a hard-hat everywhere?
On an elevator, if someone is going to the same floor you are, wait to get off, and when (s)he leaves, say "Target has left elevator. I'm in pursuit." into your watch/sleeve?
Try to start a game of Tag in a crowded area?