They Don’t Look Friendly – Rescued Kilmer’s bootleg character.
Who the Hell Are You Anyway? – Rescued Liza.
Both these achievements are obtained from rescuing npcs located in the same area. The area is hidden and only accessible once you jump a ramp.
The ramp entrance is located about halfway from Octopia to the River entrance as shown below.
Once you through and jump the ramp, you’ll find a hidden location swarming with enemy troops. Wilmer will be located in a marked prison cell and Liza will be located in the crashed helicopter as shown below.
Once rescued, the achievement will unlock for each respective character.