Follow this quick guide to gain Save Humanity and Sheeple achievements easily. For this guide to apply to you, you’ll have to be able to play level 12.
How to Obtain Look at All the Sheeple and Save Humanity Achievements
Save Humanity Achievement
For this achievement, simply set game difficulty to hard and start Level 12. (hard difficulty because we want to spend as little time in the level as possible).
Upon starting the level, simply run into all 5 humans and try not to die before collecting them all. Use Smartbombs to stay alive for this period of the level.
Once you collected all 5 (or died before collecting all 5) just let the drones kill you. That way you can quick restart the level 5 times (using the 5 provided credits).
If you are successful, you will get this achievement after about 15 – 20 Minutes, each round taking up about a minute (you probably saved some humans in the normal playthorugh as well.).
Look at All the Sheeple Achievement
For this achievement, you should probably change the difficulty back to easy, or normal. Then start Level 6 (the sheep level).
Just complete the level as usual (I personally think using the plus laser, which shoots in 4 directions, is a very easy weapon for this level).
Once you can read Wave: final on the right side of the screen (after Wave: 7) you can kill all but one sheep (there will be 12 sheep, 3 in every corner) and let the last sheep kill you for a quick restart.
You will get this achievement after about 20 – 30 minutes, each round taking up about 2 – 3 minutes.