All cars
Hit 11 Bonus Stunt items while completing Challenge 8 to unlock all cars.

All worlds
Find the Hidden Key while completing Challenge 18 to unlock all worlds.

All items
Intentionally hit at least 30 Barrels while completing Challenge 7 to unlock all items.

Upgraded laser
Successfully complete Challenge 18 on the very hard difficulty setting to unlock upgraded laser.

Infinite ammunition
Intentionally hit at least 50 Barrels while completing Challenge 18 to unlock infinite ammunition.

Infinite health
Intentionally hit at least 179 Barrels while completing Challenge 17 to unlock infinite health.

Infinite turbo
Collect 8 Zappers while completing Challenge 4 to unlock infinite turbo.

Timer speed
Intentionally hit at least 60 Barrels while completing Challenge 12 to unlock timer speed.