God Hand Fighting Ring challenges: Beat the first stage. Bonus Arena Challenges: Beat the game to unlock Arena Challenges 41 through 50. Beat those to unlock Arena Challenge 51. Hard mode: Beat the game under normal difficulty. Chihuahua Race: Beat Stage 3, then talk to the guy in the shop. Alternate costumes: Beat the game to unlock the Carnival, Devil Hand, Karate, and Olivia's Bunny Girl costumes. They can be obtained by starting from Stage 2 then talking to the new NPC in the shop.