This is a bonus mode which is unlocked once you have completed the original puzzle. The first 10 appear in the following levels:

Level 1: Rabbit.
Level 6: Tennis.
Level 15: Twelve.
Level 16: Twenty.
Level 17: Banana.
Level 23: Orange.
Level 25: Carrot.
Level 26: Potato.
Level 34: Monkey.
Level 37: Grandpa.