Do you have a "go-to" that almost always cheers them up? We do! For his entire 10 months, he has always loved when we sing "Dancin Fool" by Frank Zappa while making him dance (if he's laying down move his feet / whatever we can get to, bounce him around / twist). this works 95% of the time. I think it's sweet, & just wanted others to share.
Re: What makes them smile?
He loves being tickled and when I kiss his belly/ nom his thighs! I love his laugh, it just warms my heart.