To do this you need to do 5 backflips consecutively. And by consecutively you need to jump almost immediately after you land.
To do a backflip hold the controller in the opposite direction the player is facing and hit jump at the same time. When you land, do this again and again, the timing window is small but there's enough time to land and do a second jump. You can do this the minute you get your first female character (elizabeth most likely). But you'll need a small amount of room. You can do this in the hub world. I did it in a playable level but the room required was a little tight.