HAPPY AND YOU KNOW IT goes inside the fascinating world of pop music created for toddlers. Why do kids like what they like? Why is kids’ music so terminally uncool? Are children’s musicians the happiest people alive? Will AI soon take it over?  Featuring a colorful and charming cast — including The Wiggles, Laurie Berkner, Caspar Babypants, Divinity Roxx and Johnny Only — this documentary by Penny Lane (LISTENING TO KENNY G, HAIL SATAN?) explores an underestimated but wildly popular genre, to riotous and emotional results.  From “Itsy Bitsy Spider” to “Baby Shark,” HAPPY AND YOU KNOW IT ultimately reminds us of the magical way music connects us across generations and to the kid inside each of us.