Writing down funny things that people say and writing them just how they were said is a good writing exercise. When I taught school, I would have the kids eavesdrop and write down conversations in a notebook and then we would change the context a little, or change the words slightly to create dialogue for a story that they were working on. I like writing down quotes by my kids, and collecting them from other people I know. They make great fodder for stories 
Here are a few funny quotes by kids I know:
Alex (age 4): Mom, do you like it when people do things for you? I do, but there’s some stuff people have to do themselves – like sitting on the toilet or blowing your nose. But I wish someone could go to the bathroom for me, cause I hate going poop!
Alexisms: easy as cake, lickety slip
Alex (age 4): easy as a piece of cake.
Mom: don’t you mean easy as pie?
Alex: no, I do it in the cake kind of way.
Alex (age 4): Mooooom! Jake pinched me as hard as I dropped a rock on my toe!
Zee (age 3): Dang it!
Mom: What?
Zeeh: My Pixar! Bee just freezed it with her freezing power!
Mom: I really wish you wouldn’t have done that!
Niece (age 3): Mom, I’m not yours fairy!
