Here is the full list of all 20 Twinsen's Little Big Adventure Classic achievements.
Escape the asylum
Acquire the Magic Ball and Magic Tunic
Make the drinking water sweet as syrup
Gain the ability to speak to animals
Get the proto-pack
Give the musician a guitar in Funky Town
Get the magic saber
Visit all Islands
Finish the game
Go on 10 voyages with vehicles
Fire the canon in the museum
Get into the meca-penguin room
Talk to the Star Wars fanboy
Find the secret passage in the museum
Retrieve Lanktir’s coffee pot
Snowboard down the slopes
Become a member of the Elf Club
Escape from the prison on Principal or Proxima Island
Find all the Clover Boxes
Collect 500 Kashes