Disclaimer: Do not own Monsters, Inc. (though I do own a Sully plushie) and thank you, Zoids Fanatic, on behalf of those who'd get excited thinking Pixar is writing fanfiction.
Sully had always been tough.
You had to be, to work in the energy industry. Going out to collect screams every night when one wrong move could get you killed wasn't a job for the faint-hearted.
Still, Sully didn't consider himself to be the baddest mother in the valley. Not when there were monsters in Monstropolis that could squash him like a bug in the windscreen of life. Literally.
But monsters seemed to think he was this brave hero who was afraid of nothing and routinely risked his life to bring power to Monstropolis. Of course, the fact that he actually did so did not help at all.
Even so Sully considered himself a nice guy. His favourite past-time was shooting the breeze with Mike, he called his mother back in Monstrocity every week, and he actually liked flowers. Apart from the job, the records of screams, and the training for work, he did not understand why everyone thought he was all that badass.
It was probably the hair.
That is why he was not at all surprised when the cute little human girl named him Kitty.
Out the mouth of babes, eh?