Because Col. Sanders was chasing it with a hatchet.
Much more violent, hence funny imagery.
Nobody expects the Spanish Inquisition, not even a chicken.
You don’t need a reason why! (psst, I think the word you are looking for is “references” rather than “inferences”)
He he, see post #13. 
Why did the chicken half-cross the road? Because it wanted to get to a Rhode Island!
I don’t know about the chicken, but I do know why the dinosaur crossed the road:
Because the chicken had not evolved yet.
I could tell you, but then the Chicken Mafia would kill me.
Who said it crossed the road at all?
To get to the other side (duh).
Because shut the hell up, that’s why. Now go get me a beer, bitch.
Your momma’!
True Blue Jack
…The Aristocrats!
“Blue,” replied Salvador Dali.
The chicken crossed the road…to escape THIS CHICKEN-EATING SPIDER!! (National Geographic Link)
[Animaniacs]
*Chicken Boo, what’s the matter with you?
You don’t act like the other chickens do.
You wear a disguise to look like human guys.
But you’re not a man, you’re a chicken, Boo. *
[/Animanics]
Give me ten minutes with that chicken and we’ll find out.
– Torquemada
Well, if the chicken is an engineer, I’d say that she checked the files and this was what we did last time.
Well…
To avoid the chicken shagger