People work hard at Tough Mudder, but they don't take themselves too seriously. Everyone is pretty tightly knit, and they help each other out. The office is full of young, smart, motivated people who are dedicated to making Tough Mudder a world class event organization.
The Executive Committee does a great job of promoting a cool culture. The office is open and flowing, there's a retreat house in the Catskills, Color Wars events, ski trips, boat cruises and weekly drinks on Fridays. They do a good job of fostering the culture they value so much.
In terms of dress, it's casual. People work better and feel better when they're comfortable. No suits allowed.