I just found out about this interesting contest hosted by 
Childhood Prank
The reason my mom and I are laughing so hard in this photo, taken in East Lansing, Michigan, USA in the 1980s is because my sister and I had decided to take one of the stickers we peeled off a banana (If my memory is correct, it was a Dole brand one) and secretly stick it on my dad's back when he wasn't paying attention. Our usual routine after dinner was to go out for a walk and my dad ended up walking around with the sticker on his back, oblivious to this new "decoration" on his shirt!!
Thanks
@snooway