Animation & Sanitation

You get access to robo janitors in Chasm 24.  You can have up to 5 in a single hospital.  You get them for free by buying plots, but you don't get to choose which type you'll receive on any given plot.  If you complete Chasm 24 with 3 stars then you gain the ability to buy robo janitors and can then choose whatever you want.

This achievement may not unlock without quitting/reloading the game after having completed the objectives.