It's written as P-P-Y, but it's supposed to be an I in happiness.
5 seconds sound clip from the The Pursuit of Happyness movie soundboard.
You can hear this line at 00:16:37 in the Blu-ray version of the movie.
Quote context
[...]
- Oh. Yeah, I'm going to. So go ahead, say goodbye to it, 'cause I'm coming back without it.
- You ain't had to add the good riddance part.
- Bye.
- It's written as P-P-Y, but it's supposed to be an I in happiness.
- Uh, no. Actually, it's a noun. But it's not spelled right.
- Yeah, that's spelled right. But that's not part of the motto, so you're not supposed to learn that.
[...]