He is possibly best-known for his long runs illustrating, and later writing the Legion of Super-Heroes title in the 1980s and 1990s. He also created the alien mercenary character Lobo (with Roger Slifer), and the irreverent "want-to-be" hero, Ambush Bug. He also plotted and was breakdown artist for an Aquaman limited series and one-shot special in 1989 with writer Robert Loren Fleming and artist Curt Swan for DC Comics.
Giffen's first published work was "The Sword and The Star", a black-and-white series featured in Marvel Preview, with writer Bill Mantlo. He has worked on titles (owned by several different companies) including Woodgod, All Star Comics, Doctor Fate, Drax the Destroyer, Heckler, Nick Fury's Howling Commandos, Reign of the Zodiac, Suicide Squad, Trencher (to be re-released in a collected edition by Boom! Studios)., T.H.U.N.D.E.R. Agents, and Vext. He was also responsible for the English adaptation of the Battle Royale and Ikki Tousen manga, as well as creating "I Luv Halloween" for Tokyopop. He also worked for Dark Horse from 1994-95 on their Comics Greatest World/Dark Horse Heroes line, as the writer of two short lived series, Division 13 and co-author, with Lovern Kindzierski, of Agents of Law. For Valiant Comics, Giffen wrote XO-Manowar, Magnus, Robot Fighter, Punx and the final issue of Solar, Man of the Atom.
He took a break from the comic industry for several years, working on storyboards for television and film, including shows such as The Real Ghostbusters and Ed, Edd 'n' Eddy.
Giffen and his Justice League colleagues (J.M. DeMatteis and Kevin Maguire) have applied their humorous brand of storytelling to a title that he had drawn in the 1970s, Marvel Comics' The Defenders. The same trio are currently producing the Metal Men backup feature which appears in Doom Patrol.
Keith Giffen also collaborated with J.M. DeMatteis on the creator owned title, Hero Squared for Boom! Studios, along with artist Joe Abraham. The 2-issue mini-series Planetary Brigade also chronicled the adventures of characters originating from this series.
Keith Giffen was the breakdown artist on the DC Comic book 52, a weekly series following in the wake of the Infinite Crisis crossover (written by Geoff Johns, Greg Rucka, Mark Waid and Grant Morrison). He continued in that role with the follow-up weekly series Countdown to Final Crisis. He is also the lead writer for Marvel Comics's Annihilation event, having written the one-shot prologue, the lead-in stories in Thanos and Drax, the Silver Surfer as well as the main six issues mini-series. He also wrote the Star-Lord mini-series for the follow-up story Conquest. He currently writes Doom Patrol for DC, and is also completing an abandoned Grant Morrison plot in the Lost Year for Wildstorm.
Giffen remains a prolific creator of independent comics. Between 2005 and 2007 he's co-created and often authored or co-authored such books as 10, Tag and Hero Squared for Boom! Studios for Zapt! and I Luv Halloween for Tokyopop, Common Foe and Tabula Rasa for Desperado Publishing/Image Comics and Grunts for Arcana. Many of these were co-authored with his frequent collaborator Shannon Denton.
Giffen's art has taken on many styles over the years. His early work tended towards a heavy influence from Jack Kirby. After an early stint at Marvel, he began doing layouts for artist Wally Wood during the late 1970s revival of the Justice Society of America.
When he returned to comics after a hiatus, his style was more precise and reminiscent of George Pérez and Jim Starlin, and helped make Legion of Super-Heroes DC's second most popular comic after George Pérez's New Teen Titans. It was his work on the Legion that rocketed him to comic book artist fame and gave him a creative control with the national companies that few artists achieved. He peppered his artwork with in-jokes such as upside down Superman logos, hidden Marvel characters, eyeball creatures, and scrawled humorous messages on signs in the background of his panels in the alternate futuristic alphabet Interlac.
As Giffen's style loosened up, he found himself drawn to the work of José Muñoz (see Controversy). Soon thereafter he developed a scratchier, more impressionistic style, using a highly stlylized method of drawing directly with ink, on titles such as Trencher, Lobo Infanticide and Images Of Shadowhawk.
After his lengthy sabbatical from comics work, Giffen returned with a style that some said was influenced by his Justice League artist Kevin Maguire that was mid-way between the tight, controlled pencils of his early Legion days and the freer but less anatomically correct style he had later adopted.
For many years, Giffen would co-write comics, but only as a plotter. He relied on others such as Robert Loren Fleming, and Tom and Mary Bierbaum, to supply dialogue, even when he was basically the author of the work. He co-wrote the Freak Force series with Erik Larsen, and also co-wrote two SuperPatriot mini-series. Beginning with Trencher, Giffen started writing comics fully by himself, although he still collaborates when the project calls for it.
Giffen is known for having an unorthodox writing style, often using characters in ways not seen before. His dialogue is usually characterized by a biting wit that is seen as much less zany than dialogue provided by longtime collaborators DeMatteis and Robert Loren Fleming. That approach has brought him both criticism and admiration, as perhaps best illustrated by the mixed (although commercially successful) response to his work in DC Comics' Justice League International. His work on the 2001 version of Suicide Squad was not nearly as successful, however, and his loose, largely satirical style is considered by some a detriment to both the English version of the Battle Royale manga and to the third version of the Defenders, published in 2005-2006.
He is also known for his humorous takes on existing characters, often focusing on their personality clashes. He also has a tendency to poke fun at trends in comic books or character archetypes. His Ambush Bug miniseries is especially noted for its in-jokes such as Villian the Villain, Cheeks the Toy Wonder, and the use of DC editor Julius Schwartz as a character.
He is also known for sudden plot twists and abrupt often tragic turns of fate. During his late 1980s-early 1990s run on the Legion of Super-Heroes, light comical issues were often followed by darker ones where popular characters were maimed or killed.
Recent work includes writing The Programme #3, Dreamwar a DC/Wildstorm crossover and Reign in Hell, an eight-issue limited series, with artist Tom Derenick, about various DC Comics magical characters in Hell. On February 7, 2009, it was announced at the New York Comic Con that he would be spearheading a revival of Doom Patrol, a title which he has long said he wanted to write. He is also finishing Grant Morrison's run on The Authority and writing a Magog ongoing series. Giffen is also co-writing a 26-issue biweekly Generation Lost with Judd Winick, which will essentially see the return of Justice League International, and writing Booster Gold with DeMatteis and artist Chris Batista.
In February 1986 The Comics Journal published "The Trouble With Keith Giffen," an examination of recent dramatic changes in Giffen's drawing style (which critics and fans had largely agreed suited the strange and funny projects Giffen was then working on.). The article pointed out that Giffen had changed from a slick, clean Jim Starlin-esque style to an avant garde, heavily inked one. The article displayed several panels side-by-side to illustrate the magazine's allegation that Giffen was copying, or "swiping" the work of Argentinian cartoonist Jose Muñoz.
In response, Giffen alluded to the controversy by drawing Ambush Bug with the Peanuts character Snoopy in Son of Ambush Bug #5 (November 1986). (Giffen's frequent collaborator Robert Loren Fleming wrote the dialogue for the scene.) The controversy continued, however, when Giffen was accused of swiping Muñoz again in the anthology Taboo.
Giffen has acknowledged Muñoz's influence, and in 2000 referred to the controversy this way:
At that point in his career, Giffen was one of the most popular comic book artists in the industry, along with artists such as John Byrne, George Pérez, and Frank Miller. Although comic book artists such as Rich Buckler have engaged in swiping with the knowledge of the comic book publishers, their swiping usually involved copying panels from artwork previously published and owned by their publisher. Giffen allegedly swiped work for which his publisher, DC Comics, did not have the copyright. The ensuing controversy hurt Giffen's reputation.
Nonetheless, DC loyally protected him. They did remove him as prime artist on Ambush Bug and other titles, but gave him full-time writing duties on Justice League until the controversy was largely forgotten and a new generation of comic book fans came to discover his work. Giffen returned to drawing full-time two years later while continuing to plot the Justice League and its numerous spin-offs.
This period also marked Ambush Bug's demise as a popular major character at DC. According to Giffen, it had to do with editorial discomfort with the series' humorous approach to the DC Universe: "DC was just too uncomfortable with the (admittedly nicely selling) bully pulpit they'd provided the loose cannons on the creative team".