Place this clip at the payoff of an edit, after a downbeat setup like the SpongeBob Sad Song, so the contrast becomes the point. Follow it with a short laugh track reaction from your cast, then return to normal dialogue without another music cue underneath.
About this sound
This is about a twenty-second musical clip of Pinkie Pie singing the repeated “Smile, Smile, Smile” chorus in her high, bubbly voice. It feels relentlessly cheerful and a little over the top, turning a moment giddy, sweet or deliberately ironic. It comes from the “Smile Song” in My Little Pony: Friendship Is Magic.