When Croc was in the circus (not by his own choice) he'd made friendly-like with one of the wardens-- ringmasters, really, but he thought of them as wardens. It had just been bars after bars for him; trading sequins for orange was just cosmetic. The warden had been blind-- he moved around like Frisk did. Croc had bitten his head off and taken his keys and escaped, but not before slaughtering everyone at that circus who'd ever laughed at him.

With the exception of some of the acrobats and the other freaks, quite a lot of people.

Frisk, he realizes, is blind.

"You better run, runt!"

He dives forwards again and clips a bookshelf; books come tumbling down on him, providing Frisk with a direction not to go.