Walk up to the floating 'kit' surrounded by studs which is next to the police station in Bricksbergind and enter the following case-sensitive codes (without the quotes) to unlock the corresponding content.
Blacktron Fan and Musical Pants (Rescue Reinforcements): Enter 6LKMNDHR or HVLLRX6R
Angry Kitty and Construction Pants (Emmet’s Construct-o-Mech): Enter 6LK78NN9 or HVLH63VL
Johnny Thunder and Super Secret Pants (Super Secret Police Dropship): Enter 6LK3FRL6 or HVL4TQT4
Robo Pilot and Astro Pants: (Benny’s Spaceship) Enter 6LK3RRY4 or HVL4TB94