Very Happy Kids
From Screamer Wiki
A prank with peaceful music showing smiling and laughing happy babies. However, near the end of the video, when a baby with a man's voice saying "Make a scary face!" shows up, the baby's face turns into a scary monster's face with a loud scream in the background. Then the face goes back to normal.
Link youtube.com/watch?v=UDwIS55qX2Y
