Squirrel Girl, whose real name is Doreen Allene Green, first appeared in Marvel Super-Heroes vol. 2 #8 (cover-dated January 1992), created by writer Will Murray and artist Steve Ditko. In her debut story, the teenage Doreen ambushes Iron Man in an attempt to become his sidekick, ultimately teaming up with him to defeat Doctor Doom using her ability to command an army of squirrels. She possesses squirrel-like abilities, including superhuman strength, agility, speed, a prehensile tail, retractable knuckle spikes, and the capacity to communicate with squirrels, accompanied by her sidekick Monkey Joe. Initially conceived as a lighthearted, one-off character contrasting the dramatic tone of 1990s comics, she remained largely unused for over a decade.
Squirrel Girl resurfaced in 2005 as a key member of the Great Lakes Avengers (later renamed variants like Great Lakes X-Men or Champions), written by Dan Slott in a miniseries where she helps battle threats like Maelstrom, losing Monkey Joe in the process and gaining a new partner, Tippy-Toe. She later served as nanny to Luke Cage and Jessica Jones' daughter, joined the New Avengers briefly, and demonstrated her signature off-panel victories over major villains like Thanos and MODOK. These appearances established her as a humorous yet highly effective hero, known for resolving conflicts through wit, positivity, and squirrel armies rather than brute force.
The character's popularity surged with the launch of The Unbeatable Squirrel Girl in 2015, written by Ryan North with art by Erica Henderson (later others), running for 58 issues across two volumes until 2019. This series portrayed Doreen as a college student balancing superheroics and everyday life, emphasizing themes of friendship, self-acceptance, and non-violent problem-solving, while cementing her "unbeatable" reputation through clever defeats of cosmic threats like Galactus. Subsequent appearances in team books, graphic novels, podcasts, and games have maintained her as a beloved symbol of optimistic heroism in the Marvel Universe.