Porter:

Successfully complete the Terk challenges in world 2 to
unlock Porter in the water skiing or river surfing challenges.
Jane:

Successfully complete the Terk challenges in world 1 to
unlock Jane in the water skiing or river surfing challenges.
Terk the monkey:

Successfully complete the three Terk challenges in the
final levels of the game to unlock Terk.
Ground Tumble trick move:

Successfully complete the Terk challenges in world 1 to unlock
the Ground Tumble trick move for jungle exploration.

Scarecrow trick move:

Successfully complete the Terk challenges in world 2 to unlock
the Scarecrow trick move for the water skiing challenges.
Corkscrew trick move:

Successfully complete the Terk challenges in world 3 to unlock
the Corkscrew trick move for the river surfing challenges.


Hidden FMV sequence:

To get see a hidden FMV sequence about Tarzan, collect all 75
Film Reels.