Map: Goat Bay City
Near the large skyscraper and roller coaster, you'll find a bridge over the water.
Facing the roller coaster side, you'll see a drain/sewer pipe below and to the right of the bridge.
Simply enter the pipe and you'll be taken to the sewer immediately unlocking the Disgusting Achievement
Walk forward and enter the tunnel on the left and you'll see the 4 "turtles"
Ram/Head butt/lick them all and you'll unlock the Ling Ling Into Battle Go Achievement