Moose's character is the only one that appears in nearly all the films. He is shown in Step up: The Streets as a secondary character, Step Up: 3D as a main character and Step Up: Revolution as a guest character. Camille (Alyson Stoner) despite being his love interest, is shown in the original Step Up and Step Up: 3D.
During the final dance scene, when the guy doing the kick boxing moves slides across the floor on his knees he splits his pants, which are then repaired the next time he's shown.