Tony Hawk's Underground, abbreviated to THUG, is a skateboarding video game, developed by Neversoft and published by Activision in 2003 for the PlayStation 2, GameCube, Game Boy Advance, and Xbox platforms. A PC version was released exclusively in Australia as a budget release in 2005, ported by Beenox.[citation needed] In 2004, its sequel was released. It is the fifth game in the Tony Hawk's series, and the first not to bear the Pro Skater suffix. It features the ability to create a custom character, and supports face mapping and online play on the PS2 and PC versions. Unlike its predecessors, Underground focuses heavily on its story mode, plus is also the first game in the series to introduce the ability to travel around levels on foot.

"little" Tony explores the white to blue belt curriculum for Brazilian Jiu-Jitsu focusing on a strong foundation in the 3 aspects of the Art: Self-Defense, Street Combatives, and Sport Brazilian Jiu-Jitsu (Gi and No-Gi). Each section has the basic theory, philosophy and approach explained so each student can pursue future rankings and competitions. This is the same curriculum "little" Tony uses for promotions of his students around the world.