Mini-games:
Collect the hidden icon in the listed location to unlock the corresponding mini-game.

Aeronauts: Secret room in level 4. 
Apple Masher: Secret room on top of the haystacks in level 3. 
Bale Out: Secret room in Zuckerman's Barn. 
Bounce: Enter the hole in the tree and search in the branches in level 8. 
Bumper Cars: Ledge outside the circus tent in level 13. 
Food Catch: Enter the tires and look on the tire pile in level 10. 
Ring Toss: Secret room outside the circus tent in level 14. 
Snacktime for Templeton: Enter the tires and look on the tire pile in level 9. 
Spree Ball: On top of the Information Booth in level 14. 
Water Fun: Enter the hole in the tree and search the branches in level 5. 
Webbing Crashers: Secret room next to the water wheel in level 6.