Perform the following to unlock the aliens.
| Alien | How to unlock
|
|---|
| Aerodactyle | Complete Level 2: Mess Hall Mashup.
|
| Big Chill | Complete Level 3: Welcome to Erf.
|
| Bullfrag | Complete Level 2: Mess Hall Mashup.
|
| Cannonbolt | Complete Level 5: Core of the Problem.
|
| Gravattack | Complete Level 4: Underground and Beyond.
|
| Swampfire | Complete Level 1: Stow Away.
|
| XLR8 | Complete Level 4: Underground and Beyond.
|
