Carlos

Carlos is one of Rico's sons. He can be found in Lower East Quack.

How to Rescue
There are two ways to reach him, though one is significantly easier than the other.

The first is to hitch a ride on the underground subway whilst already playing as Rico and leap off when you see him. The other, simpler way is to reach the exit of the level, use the Rico telepoint and open the gate to Upper East Quack. It leads a straight route to the same area.