Mary and Fred are two exceedingly unintelligent aliens of an unknown species who make a living out of capturing and collecting alien specimens. It is important to note that "Mary" and "Fred" are not their real names; rather, they were the names they had written on the name tags of their "human" disguises. Mary speaks with a stereotypical 'hillbilly' accent; he constantly refers to Fred as 'Pa'. Fred, however, speaks with more of a Cockney British accent.
Their species are brownish-green in color, and have solid-colored eyes, similar to an Irken's. They are very tall, and their shoulders go up to their heads.
Mary and Fred travel around in a huge cloaking device-equipped spaceship, abducting both sentient and non-sentient creatures and performing "experiments" on them. However, all of their specimens have easily escaped, save one, who has been "fused" (duct taped) to various items by Mary and Fred and lacks the limbs necessary to leave his containment tube.
On their visit to Earth, they encountered Zim, and claimed to be his new neighbours while their spaceship knocked out Zim's communication field, interrupting his conversation with the Tallest. However, Zim quickly saw through their pitiful disguises and called them out as aliens; Fred quickly resorted to "Plan two", which was to stuff Zim and GIR in a sack, and take them up.
Once aboard their spaceship, the aliens stated their intention to perform a "fusion" experiment on Zim, which involved fusing him "to another human being." The exasperated Irken attempted to make them understand that he wasn't human (going so far as to remove his and GIR's disguises), but even obvious facts weren't strong enough to break through their thick skulls. Eventually, the two abductors decided to carry out the experiment anyway, which turned put to be far more pathetic than it sounded: in actuality, the "human" they had was really a gopher, and all they did was duct-tape it to Zim's head. Eventually, Zim managed to distract his abductors by directing their attention toward the ceiling, and easily managed to leave the ship with GIR in one of the escape pods; throughout the chase, Mary and Fred's efforts to recover their specimens can only be described as minimal; even when they were standing outside the open hatch to Zim and GIR's pod, they merely pawed at them halfheartedly.
As alien abductors, Mary and Fred are ludicrously inept, ignorant and unintelligent; they are very easily fooled, yet place complete faith in their own, horribly incorrect misconceptions. Moreover, they often lament the fact that all of their specimens escape, yet they do absolutely nothing to fix the facts that their containment tubes can be easily opened and exited from the inside, and their ship has absolutely nothing in the way of security.
Mary and Fred seem to have a limited understanding, if any at all, of humans, Earth, and the universe in general. They have not heard of the Irken Empire, as they "don't get that TV no more". Mary seems to have an obsession with fusing things to Fred's juice, as Fred stated: "Look, I'm the captain, and I'm sick of you always fusing things to my juice!".
They both appeared in Jhonen Vasquez's earlier work, Johnny the Homicidal Maniac. They abducted a man and told him to mate with a female of his kind. This female turned out to be a chicken. Later, they abducted Squee.
They made their only appearance in "Abducted". At the end of the episode, they are seen abducting Dib, thinking that he is a specimen of a weasel.
- Mary: Heuuuehuahuauauhuueaoeueyy YEAH! The dog! Explain it!
- Howdy, Squishy! We would like to vomit language in your shelter unit!
- Aw, now the dog's escaped! Look at him go.
- They were voiced by Eric Trueheart and Paul Greenberg. However, takes were done of Brian George and Jim Wise; due to an audio mix-up, these weren't included, but Wise and George are still credited as the voice actors in the episode.
- According to Jhonen Vasquez and Steve Ressel in their respective commentaries, the crew originally sought to get Monty Python members John Cleese and Eric Idle to do the voices of the Abductors, when Cleese declined, it was then sought to get Terry Jones. In the end, none of them agreed to contribute.
- As noted above, their real names are unknown. Because of this, some fans have taken to calling them "Blue" and "Green", in reference to their respective eye colors.