Flock

Infinite boost
Get at least a Gold medal on all single player levels to get unlimited boost.

Blanka boulder
Successfully complete Campaign mode with a perfect abduction on all single player levels.

Awards
Successfully complete the indicated task to get the corresponding award:

Chicken trophy: Get a Bronze medal or better on all single player levels.
Cow trophy: Get a Gold medal or better on all single player levels.
Pig trophy: Get a Silver medal or better on all single player levels.
Sheep trophy: Get a perfect abduction on all single player levels.

Close Encounters Of Third Kind reference
At the level selection screen, hover over the options for levels one through five in order to hear the notes that were played in Close Encounters Of The Third Kind.

Trophies
Successfully complete one of the following tasks to get a trophy:

First Flock! (Bronze): Completed first level.
Lumberjack The Ripper (Bronze): Rip up 50 trees (aggregate total).
The Continuous Cartographer (Bronze): Play through one user-created singleplayer level and one user-created multiplayer level.
Unidentified Flocking Object (Bronze): Abduct 20 animals (aggregate total).
Fertiliser (Bronze): Make 50 piles of poo (aggregate total).
Good Shepherd (Bronze): Flock 25 animals at once.
Don't Fence Me In (Bronze): Knock over 50 fences with a cow (aggregate total).
King Of The Skies (Bronze): Fly and land 75 chickens (aggregate total).
Make Your Mark (Bronze): Complete 10 crop circles (aggregate total).
Love Bunny (Silver): Use 3 love patches in 3 minutes.
Bowled Over (Silver): Kill 10 chickens with one throw of a boulder - strike!.
Defender Of The Flock (Silver): Complete a level featuring the night-time predator without letting it eat any animals.
Master Flocker (Gold): Get a perfect abduction on all levels, singleplayer and multiplayer.