Robby has had a little stuffed monkey since he was about 3 1/2 months old. We put him to bed with the monkey but that was about it. Last week, I decided to give it to him before we left the apartment and he just latched on to him. He now wants Monkey to tag along while he plays, while he rides in the car, while we shop at the grocery store, etc. We just call him "Monkey" so when we ask Robby if he wants Monkey, Robby replies by saying "kai-kai" although at some times it sounds like "guy-guy" and other times he'll actually say "key-key", but usually it's "kai-kai". Anytime we hand Monkey to Robby, Robby puts Monkey's mouth right into his own and gives him a good bite. Here is a video of how he greets Monkey (I was trying to get him to say "monkey" because he had just been saying it!)
Here I finally am able to get him to say it at almost the end of the video. I promise you he says it every time we give Monkey to him, unless I'm videoing him, of course!