Shredder's Revenge is packed with hidden collectibles that reward you with points, unlock character upgrades, and contribute to your overall completion percentage. There are several types of collectibles to look out for:

- Disgusting Bugs: These creepy crawlies are often hidden in destructible objects like vending machines, trash cans, or behind scenery. Collecting them contributes to a specific challenge.
- Secret Diaries: Small notebooks that reveal lore or humorous insights. They are usually well-hidden in less obvious destructible objects or tucked away in corners.
- VHS Tapes: These classic tapes unlock concept art or character profiles in the Extras menu. They are typically found in more challenging-to-reach spots or after defeating specific enemy waves.
- Crystal Shards: These glowing shards are often dropped by specific mini-bosses or found in secret areas. Collecting a certain number can unlock new special moves or character upgrades.
- Cameos: Certain stages feature background characters from the TMNT universe. Interacting with them (usually by walking near them) can trigger a small animation and count towards a challenge.
Always smash every destructible object and explore off the beaten path to maximize your chances of finding these hidden treasures. The game often provides subtle visual cues or sound effects when a collectible is nearby.