Here is the full list of all 12 Sam & Max: Beyond Time and Space achievements.
Won all upgrades for the DeSoto.
Completed episode 5.
Completed Sam & Max: Beyond Time and Space.
Witnessed Satan berating the staff each time hell efficiency dropped.
Completed episode 4.
Tried every dialog choice with all AI personalities.
Tried every possible body part on the monster.
Completed episode 3.
Completed episode 2.
Offered the granite sandwich to everyone on the island.
Completed episode 1.
Celebrated the bug's birthday before his family arrived.