Cough

Here’s something:  Elliot loves coughing.  He’ll cough, and then he’ll laugh because apparently coughs are funny, and when he laughs it's kind of a laugh-cough, which is even more funny to him, so he’ll laugh at that, which produces an even bigger laugh-cough, and well that's outright hilarious, and triggers more laugh-coughing, and so on.

Here’s something else:  It doesn’t have to start with a real cough.  He will make himself cough—you can hear that it’s fake, it’s obvious!— but he doesn’t care, he still thinks it’s funny and it starts the cycle going. 

It’s pretty adorable to watch.  He’ll be sitting, playing, and from somewhere down in that nectarine of gray matter will emerge the idea to start coughing.  And he’ll just go for it, coughing and laughing and coughing.  And for the next few minutes he’ll just entertain himself with his own bodily functions.

Which, now that I think about it, is not all that abnormal.