Will is pretty used to dealing with people with... unique physiology, shall we say. He might not have been so eager to get into the carriage with Quatre if he'd had the head of a lion to go with the rest of him, but his top part seems human-like so Will is working with the assumption Quatre doesn't just go around killing people.

In any case, he's comfortable enough to grin reassuringly at Quatre's statement. "It's not your fault whoever does the maintenance around here wasn't paying attention today."

Talking is a distraction from thinking about exactly how high up they are right now.