There are 10 Trophies that can be earned in this title.

Bronze

Bad Cop/Sad Cop
Threaten and 'Noir' everyone you meet on the street in Act 1

The Grand Tour
Explore the museum completely

Blimp's Eye View
Turn into the Hindenburg in every room and get a bird's eye view of the environment

Tweenage Angst
Have Sammunmak banish every possible object in Act 3

Drop a Dime
Teleport to every phone in the museum

Silver

Pound the Pavement
Tracked Max's brain-thieves to the Museum

Saboteur!
Foiled an evil alliance and recovered Max's brain

All Hail Sammun-Mak
Infiltrated the boy-king's inner circle

Rhinoplastastic
Turned into every possible object

Gold

Reunited (And it Feels So Good)
Lobotomized the Pharaoh and got Max his brain

http://www.ps3trophies.org/game/sam-and-max-the-devils-playhouse-3/trophies/