Out of Space: Couch Edition

As the description says, this achievement is earned by not killing any aliens (putting them in the recycler or throwing them off the ship at the start of the level). Using water or the mop on them is okay. The dog (earned by playing solo once) was the key strategy for this achievement since feeding aliens to the dog doesn't count as killing them. You can also deal with aliens by placing them on a table or in a refrigerator (untested) if you happen to find one.

I knocked this one out in co-op with two other players on a medium sized ship. Our strategy was to rush as many rooms as possible at the start of a machine. If you do this, most of the rooms will be clear of aliens since they slowly spawn from eggs over time. Our goal was to take control over about half of the rooms this way then focus on making money with exercise bikes. From there, we would rush into a single room and knock out all of the aliens then feed them one-by-one to the dog.