I used to work at a state-run living facility for mentally retarded adults. This was an easy job. My job was to do activities with the clients, then to bathe them and put them to bed. During the night I would change their bed linens if they wet or soiled themselves. In this sense it was like working in a nursing home. In the morning I would wake them and dress them.
It was said that their IQs were in the 20 range. (At least that was the case for most of the ones I worked with.) Though it's hard to measure IQ at that level. Most of them never learned how to speak, and some of them never learned how to properly walk.
They were all idiosyncratic and much more original than people with normal intelligence. One of the male clients would twirl around and push whoever he was nearest to when he stopped twirling. One day he did this and he pushed one of the female clients. She fell and broke her nose on the asphalt. She didn't know how to brace herself for the fall. We take it for granted that if we fall we will put our hands out in front of our bodies to keep from making an impact with the ground. She had never learned how to do that, so she broke her nose.