Microwave Adaptive Range Christmas Obliterator
M.A.R.C.O. is a contraption roughly the size of a doghouse. It is designed to emit microwave rays which can be focused and aimed at targets of different sizes and at different distances up to several hundred yards. The microwaves themselves are generated by a special coil which Nimnul bought from an unknown source in Arkham, Massachusetts, and which is apparently not available anywhere else. It is protected by a metal casing which gives the whole apparatus a science-fiction B-movie-like appearance.
When not in use, M.A.R.C.O. is covered with a case which makes it look like a big Christmas present, complete with decorative paper and a green bow on top to which a tag with the machine's acronym is tied. Despite its size, Nimnul is able to carry it even when it is closed.
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Driven by Christmas hatred, Nimnul uses M.A.R.C.O. from a temporary lair in a soon-to-be-demolished house where it is placed on a pair of aluminum brackets mounted on a balcony railing. His first target is a small frozen pond which is used as an ice-skating rink. M.A.R.C.O.'s microwaves melt the ice on the whole pond within less than a minute and causes the skaters to fall into the water. Stan Blather reports this incident on TV, and the Rangers decide to investigate. When they arrive at the scene, the pond is frozen again, but Nimnul melts it once more, then he shoots out a nearby row of park lights by overloading the bulbs. Next, he sets an undecorated Christmas tree for sale on fire. The flames spread to other trees, and eventually, the gum in the first tree explodes while the Rangers are flying past nearby, damaging the Ranger Plane.
The Rangers manage to discover the source of all the havoc in time and decide to stop it once and for all before Nimnul can destroy the next target, but M.A.R.C.O. is faster than them—its main coil burns through, and Nimnul has to go and acquire a new one the following day which will take him several hours due to the heavy pre-Christmas traffic in and around New York City. The Rangers plan to disable it the same day when Nimnul is away. However, the professor discovers them when he returns to get his money which he forgot and locks them away in a bottle. It is Gadget (who has not been with the Rangers until then) who liberates them and modifies it to destroy itself. She declares Dale's suggestion to reverse the polarity to not going to work. Instead, she reduces M.A.R.C.O.'s range so extremely that it can target its own interior which it does when Nimnul aims at the giant Christmas tree in front of the Rockefeller Center, so he burns his hands on the hot casing. When Nimnul finds the Rangers to be running free, he tries to shoot them, but the shortened range causes M.A.R.C.O. to shoot backwards. The rays go right through Nimnul, and after they have been reflected multiple times, they hit a stack of cardboard boxes which contain Nimnul's self-invented Super Extremely Unadhesive Soft Soap. At the same time, the machine emits a 911 dial tone which is caught by the illegally installed telephone. When the police arrive, Nimnul has no chance to get away safely due to the soap spread on the floor.
M.A.R.C.O.'s further fate remains unknown as of now.