There are 7 "worlds" in the game, each with 2 or 3 levels. Once you complete World 5's two levels and see the memory of the two kids at the museum you "Can" get this Achievement.
I say "can" because you have to find it in the memory. While the memory plays you can move left or right to play the memory or rewind it. Keep playing through it until an object in the area shakes and makes a sound, once that happens freeze on that scene and a little box will appear and unlock the Achievement.
In order to get this one, you have to rewind until the egg in the background starts to shake, then freeze the screen to let the little box hatch out of it. Below is a video for reference.