Carl is a UN soldier who in 1967 was on board a ship nearing Mondo Island. Nelson had read many works on the island, and its rumored inhabitant King Kong. Nelson eventually decides to stop on the islands, and takes his subordinates Susan Watson and Jiro Nomura with him. On the island, Carl and Nomura are warded off by a native of the island. They go to investigate, but are stopped by Watson's screams. Carl and his Lieutenant come back down the mountain to discover that while they were gone, Watson had been attacked by Gorosaurus and rescued by Kong, who had now grown attached to her. Nelson and Nomura eventually are able to escape with Ms. Watson when She makes the ape put her down. Back on the ship, Nelson is summoned to the Arctic by his ex-colleague Doctor Hu. Carl takes the ship to him, but they are kidnapped by Hu, and held captive. Nelson receives favored treatment from his Lieutenants, often being invited out of their cell for various reasons. during a chess match with Hu, Carl is informed that the temperature in their cell had been set to zero, and his friends would die if Carl did not help Hu control King Kong. Nelson is unable to reply, as at that time King Kong escaped from his subterranean cell, causing the base to collapse. Nelson and his crew are able to return to the ship, but they soon learn that Kong is headed to Tokyo, where he will fight Hu's Mechani-Kong. When Nelson reaches Tokyo, he tells the advancing Japanese military that they should try to lure the battling Kongs away from the city. The military complies, and Mechani-Kong is defeated with no casualties. Nelson watches as King Kong swims away back to Mondo Island.
- Carl Nelson may be the designer of Mechani-Kong.