Played by British-born Canadian actor David Hewlett, McKay was a main character in all five seasons of Stargate Atlantis (2004–2009).

His next appearances in Stargate SG-1 were in Alternate timeline and different realities until the crossover episode "The Pegasus Project" in season ten.

[6] McKay originally turned to science after his piano teacher told him he was a "fine clinical player" but had no sense of the art.

In "48 Hours", he is assigned to help Major Carter recover Teal'c from being trapped in the Stargate, but McKay's theories are proven wrong.

[13] He leaves his apartment and a cat on Earth,[14] and becomes the expedition's leading expert on the Ancients, and is assigned to an exploration team consisting of Major John Sheppard, Teyla Emmagan and Lieutenant Aiden Ford.

[9] McKay's problems attempting to resurrect Project Arcturus cause him to seek the help of his sister, Jeannie Miller, a fellow scientist whose intelligence matches his—but who lacks the worst of his most aggravating personal qualities.

During this time, Rodney invents several equipment upgrades, writes several theories and books, including a biography of Dr. Weir, and optimizes the city's power grid, believing himself a dead man.

After accepting that Ascension is his only hope of surviving, Rodney attempts to make amends to his colleagues and gives final gifts to several friends, including healing the massive scarring on Ronon's back.

[20] "Reunion" shows McKay deflated when the newly promoted Colonel Samantha Carter is announced as the new leader of Atlantis after Dr. Weir's condition worsened.

[22] Katie and Rodney are no longer speaking in "Trio" because she interpreted his recent decision as a break-up and lack of interest, and she adds her name to a list to be transferred back to Earth.

[23] In an alternate future in the season finale episode, "The Last Man", McKay loses Sheppard, Teyla, Ronon, and Carter, quits the Atlantis expedition team and becomes romantically involved with Dr.

[19] Although McKay enjoys deriding medicine as voodoo and fake science, he considered Dr. Carson Beckett to be "the closest thing to a best friend" he ever had.

[11] McKay is a hypochondriac, claiming at various times to suffer from hypoglycemia,[29] restless leg syndrome,[30] allergy to bee stings[31] and citrus fruit,[12] none of which have ever been confirmed.

[32] He studied medical science at one time, but stopped because too much information on the human body made him start diagnosing himself with many phantom diseases.

[35] Despite his shortcomings, McKay has performed acts of genuine courage, overcoming his own fears to, for instance hand-carry, and then throw, a naquadah generator through the Stargate in order to lure a creature of floating energy out of the city (Although it should be said he was wearing an impenetrable personal force field at the time), or evacuate entire populations from planets about to be destroyed.

[31] He often provides comic relief in addition to his considerable technological expertise, and his ability to find solutions in situations of imminent death have been used against him several times to motivate him.

[12] He named the people of Geldar after a blonde girl he once dated, and went so far as advising the women to wear their hair in a manner similar to Col. Carter's.

[39] Producer Joseph Mallozzi described McKay as "an insufferable ass [in "48 Hours"] who, over the course of the franchise's run, ended up redeeming himself in surprising fashion.