The product of a Cold War era U.S. military experiment, Doop was instrumental in the fall of the Soviet Union. Little is known of Doop’s whereabouts between that period and his recent job as cameraman for the media-savvy, profit-driven mutant superteam X-Force, but at some point he befriended Wolverine and possibly became a priest. Doop's unique look and quirky personality made him arguably X-Force's most popular member, with Doop merchandise everywhere. One of the few X-Force members to survive the Boyz R Us massacre, Doop immediately took to the new team leader, Mister Sensitive. When former team manager the Coach betrayed U-Go Girl and Mister Sensitive, Doop convinced Wolverine to intervene on their behalf. Curiously, Doop was unaffected by Lacuna’s time-altering powers when she sought membership. Accidentally sending his teammates into his own psychedelic nightmare dimension after popping a zit, Doop entered it himself to rescue them, although no one remembered these events. After following U-Go Girl’s death, Mister Sensitive rechristened their group from "X-Force" to "X-Statix" at the opening of the Doop Children’s Hospital.
During new membership tryouts, Doop discovered the applicant Corkscrew was suffering from Code-X, which made him dangerously unstable, and later killed him. When many believed Mister Sensitive had become the villainous Bad Guy, Doop defended him. Sent by Spike Freeman to see if Wolverine had Code-X and to deal with him if he did, Doop was unaware Wolverine was sent on a similar mission by Charles Xavier. The duo briefly fought before teaming up to rescue the mythical Pink Lady from her captor Hunter Joe, whose head was later mounted on Doop's wall. After photographs of El Guapo’s affairs leaked to the press, the furious teammate rightfully blamed Doop. During a dinner meeting, Doop viciously murdered an assassin sent to kill Henrietta Hunter. After Spike Freeman’s death, Doop was one of the team members sent to Russia to find a new financier for X-Statix. Kidnapped by Russian terrorists, Doop’s brain exploded during a scuffle between X-Statix and the Avengers. The two teams battled each other in an attempt to reassemble Doop’s brain, until only one piece remained. Animated by the temporary backup brain in his butt, Doop battled Thor for the final piece of his brain. Finally recognizing X-Statix as heroes, the Avengers handed over the brain. X-Statix later resolved to break up following one final mission, during which every member, Doop included, apparently died. Doop's popularity endures despite his seeming demise, as evidenced by sales of "Doop Lives" t-shirts.
It appears that Doop has recently returned to Earth from outer space, but it is unknown whether this creature, which Polaris identified as Daap, is a different being altogether or if Polaris simply misheard the complex series of clucks and barks that constitute the alien language as Daap instead of Doop. The truth may never be known.