She is Commander Repeatski's daughter and has special boomerangs to protect her. You can fire these boomerangs at enemies also. She can be found in the Post-Apocalyptic World 199X, Level 1, you can save her after completing the chapter.
Unlock Dolphin Lundgren:
In 9600 BC you will find logs falling along with the waterfall, go up by jumping on the logs and then jump to the right corner. Here you will see a door, shoot it. Dolphin Lundgren will be inside along with few soldiers, kill them and rescue Dolphin Lundgren, who has a huge machine gun for long-range attacks and echolocation energy attack for short-range burst attacks.
Unlock Jef Leppard:
You will find Jef Leppard, who shoots long-range rockets and throws grenades, half way through Chapter 1 – 198X. He will be on the other side of the locked gate. You will see that a robot is trying to kill Jef by shooting him; you have to kill that robot before it kills Jef. Rewind the game twice to get sufficient firepower that will destroy the wall and the robot. You can walk up to Jef and save him after you kill the robot.
Zackasaurus can Skateboard with the bottom of it which helps to block incoming bullets. He can also spit a long-range purple acid, which remains at the same place to cause further damage and a close-range dino bite attack. Zackasaurus can be found in the last chapter of 1,000,000 BC level. To save him, shoot the T-Rex to destroy the eggs between Zackasaurus and yourself. Rewind the game to gain enough firepower and quickly save Zackasaurus before he is eaten up by the T-Rex.
Unlock Lou Don Jim:
You will find Lou Don Jim in the year 3072 on the second level of the breakable floor. You can reach there through a vent of the hallway. Dodge fires and find the breakable floor. Touch Lou Don Jim and he will be unlocked.
Unlock Squirty Harry
Currently we don't know the procedure to unlock Squirty Harry, we will update the procedure soon here, in mean time if you find a way, please feel free to comment so that we can update here.