Complete the indicated task to unlock the corresponding character.

Character	How to unlock
Cleo	In 199X, catch up to her.
Dolphin Lundgren	In 9,600 BC, reach the waterfall with the falling logs. Ride the logs down instead of moving up, then jump to the bottom right corner of the area to find a door. Shoot it open and kill the enemy inside.
Jef Leppard	In 198X, search for his cage behind a large gate. An enemy robot will drop down. Quickly defeat the robot before it kills Jef to save him.
Lou Don Jim	In 3072, blow open the vent cover and enter the hallway. While avoiding the fires, look for a breakable floor. Destroy the panel, followed by a second panel to find Lou.
Zackasaurus	In 1,000,000 BC, you will encounter Zack tagging dino eggs before reaching the Boss. Defeat the killer dinosaurs to save Zack.