What's a song that instantly makes you smile?

I'm sure it sounds cliche, but this song is special to me. I had a young friend once. He was about 8 when he introduced himself to me one day while I was outside cleaning up after the dogs. We clicked right away and he became an important part of my life.

This song was popular around that time, and he mentioned it in a short note he scrawled for me telling me I was his friend and to remember the song "Happy". And so, I remember the song "Happy".

I learned this summer he's going to be a father soon. In my mind he's still too young for that, but I know he'll be a caring dad who'll do his best.