Here is a video walkthrough and a short step-by-step guide.
1) Start with the ‘Mascot Outfit - Stands’ and set the difficulty to casual.
2) Go the ‘Thwack’ stand and pick up the picture of a Flamingo on the table.
3) Go to the parking area and get a keycard from a security guy (subdue) in the Parking security by turning off the fusebox outside on the wall
4) Find the Flamingo Mascot near the Parking security and subdue him! (NOT KILLING!)
5) Drag the Flamingo Mascot the entire way up to the Pallas room
6) Inside the room drag the Flamingo Mascot in middle of the room
7) Use the flamingo photo on the robotor and the achievement unlocks.
(Credit to Zasta 360GameTV)