Ivan Avi

Ivan Avi, also known as The Palindrome, was actually two separate men (both named Ivan Avi) who lived at 1997 Plissken Circle.

Good Ivan
Good Ivan Avi was born in the Mirror Universe, and was distinctly out of place; he was a kind-hearted, artistic soul in a cruel, soulless, corporation-dominated world. When he was thirteen, he suffered a freak limbo accident at his Bar Mitzvah, which destroyed his pineal gland and allowed him psychic access to the thoughts of his evil twin.

Over time, the two were able to communicate (Evil Ivan had also lost his pineal gland in a freak limbo accident), and pooled their talents to create a quantum singularity machine. Using it, they intended to change places; Good Ivan would be allowed to live in the normal universe, with its anti-trust laws and non-aerosolized soup, while Evil Ivan would move to the mirror universe, where his cruelty would fit in better.

Unfortunately, while the two were changing places, Wendy Watson was sucked through the quantum singularity as well, into the mirror universe. When confronted by the Middleman, Good Ivan destroyed his quantum singularity machine, terrified that he would be made to return to the mirror universe. However, once he discovered what had happened to Wendy, he was struck with remorse and helped the Middleman rescue Wendy.

Good Ivan was a thin, nervous man, clean-shaven and dressed in a light gray suit. He was also very talkative, expounding on his plan for the "one-for-one Ivan exchange" at length to the Middleman.

Evil Ivan
Evil Ivan was born in the normal universe, and grew to detest its kindness. After suffering his freak limbo accident, he wished to trade places with Good Ivan in the mirror universe, where he would fit in better.

In the process, Wendy was sucked through to the mirror universe as well. She enlisted the aid of the Mirror Middleman to track down Ivan, who also destroyed his quantum singularity machine. Wendy and the Middleman arrested Ivan and took him to Middleman Headquarters for interrogation.

In the interrogation room, he received a psychic message from Good Ivan, conveying the knowledge of how Wendy could return to her universe. Under the pretense of having more to tell her, he lured Wendy close, grabbed her Middle-Gun, and held her briefly at gunpoint to name his terms. Rather than listen, the Middleman shot him in the face, killing him instantly.

Evil Ivan had a mustache and goatee, and wore a dark suit. He had very little to say about himself, and seemed to find excessive conversation annoying.

"The Palindrome"
While Evil Ivan was stealing the necessary components of his quantum singularity machine, the Middleman and Wendy tracked him. At each location, Evil Ivan left an image on a mirror based on Good Ivan's instructions:
 * At the maximum security medical facility where he stole the beryllium sphere: a stick figure ("a man")
 * At DARPA's Midwestern auto lab, where he stole an oscillation overthruster: a light bulb ("a plan")
 * At the toy factory where he stole eyes made of polydichloric euthimal: two waves ("a canal")
 * At the Carpenter Road Transformer Station, where the exchange of Ivans took place: a Panama hat ("Panama")

Put together, the four clues say the classic palindrome (same phrase forward and backward), "A man, a plan, a canal, Panama." After discovering the first three mirrors, Wendy and the Middleman figured out the message Good Ivan was conveying and nicknamed their mysterious quarry "The Palindrome".

After capturing Good Ivan, the Middleman inquired about the palindrome message. Rather than it being some deep and meaningful message about mirror universes, Good Ivan revealed that he simply left it because he "always wanted to be an artist".