This Seeking Tech guide will explain how you can unlock the Throwback Outfit and the original DualShock controller skin in Astro Bot.
Both of these can only be unlocked after you find 120 puzzle pieces, in addition to rescuing at least 300 characters.
Afterwards, head over to the north side of the Crash Site and then build a wall. You should then be able to access the Great Master Challenge. By beating this stage, you should get the Throwback outfit and Gen 1 Dual Speeder as rewards.