Here is the full list of all 38 Pitfall Planet achievements.
Buy 5 hats.
Buy your first hat.
Collect all the gems in the Dead Caverns.
Complete the Dead Caverns.
Collect all the gems in the Factory.
Complete the Factory.
Complete Greenwood Falls.
Collect all the gems in Greenwood Falls.
Complete Sewage Treatment.
Collect all the gems in Sewage Treatment.
Throw your friend off within 10 seconds of starting a level.
Find the frozen miner.
Complete the Outpost.
Collect all the gems in the Outpost.
Collect all the gems in the Tutorial Caves.
Complete the Tutorial Caves.
Complete every level in Pitfall Planet.
Collect every gem in Pitfall Planet.
You've bought all the hats!
Complete the Chimney.
Collect all the gems in the Chimney.
Complete the Mountainside.
Collect all the gems in the Mountainside.
Complete the Dead Desert.
Collect all the gems in the Dead Desert.
Complete the Rose Caverns.
Collect all the gems in the Rose Caverns.
Complete the Old Watchtower.
Collect all the gems in the Old Watchtower.
Complete the Mountain Core.
Collect all the gems in the Mountain Core.
Find the hidden gem cave.
Find the secret arcade.
Complete the game while always getting both players into the elevator.
Seriously, what's up with that?
Beat the race challenge in 30 seconds.
Reunite all the missing astrobots.
Find Kate's launchpad and her final diary entry.