Aliens can be unlocked by satisfying the corresponding requirements indicated below.
| Unlockable | How to unlock
|
|---|
| - Finish Level 2: Mess Hall Mashup.
|
| - Finish Level 3: Welcome to Erf.
|
| - Finish Level 2: Mess Hall Mashup.
|
| - Finish Level 5: Core of the Problem.
|
| - Finish Level 4: Underground and Beyond.
|
| - Finish Level 1: Stow Away.
|
| - Finish Level 4: Underground and Beyond.
|
