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