Here is the full list of all 20 Crazy Alien achievements.
Save 1 animal
Save 2 animals
Rescue 3 animals
Rescue 4 animals
Rescue 5 animals
Rescue 6 animals
Rescue 7 animals
Rescue 8 animals
Rescue 9 animals
Rescue 10 animals
Rescue 11 animals
Rescue 12 animals
Rescue 13 animals
Save 14 animals
Rescue 15 animals
Rescue 16 animals
Rescue 17 animals
Rescue 18 animals
Rescue 19 animals
Rescue 20 animals