In 2000, Immonen was one of the founders of Gorilla Comics, a company formed with Mark Waid, Kurt Busiek and several others. Immonen and Busiek collaborated on the "Shockrockets" limited series and the "Superstar: As Seen on TV" one-shot but the company folded after a short time. In 2005, Immonen published "50 Reasons to Stop Sketching at Conventions", a series of fifty comics that detail why he no longer does sketches for fans. Besides self-publishing, Immonen also maintains a webcomic called "Never as Bad as You Think" which is co-authored by his wife, Kathryn. "Moving Pictures" - a webcomic co-authored by the Immonens - was published as a graphic novel by Top Shelf Productions in 2010. Immonen illustrated Marvel Comics' "Ultimate Spider-Man" from issue #111 to issue #133. He subsequently worked on "The New Avengers" from issue #55 to issue #64. He continued to be the series artist when "The New Avengers" relaunched during the "Heroic Age" storyline and was the regular artist for the first seven issues as well as issue #11. In 2011 Immonen illustrated Marvel's "Fear Itself" miniseries which formed the core of a company-wide crossover storyline of the same name. In November 2012 he and writer Brian Michael Bendis started the series "All-New X-Men". In 2010, Immonen won the Joe Shuster Award for Outstanding Artist. Doug Zawisza, reviewing the 2011 "Fear Itself" miniseries for Comic Book Resources, praised Immonen's art. He consistently singled out Immonen for his simple but detailed storytelling, and his ability to render varied subject matter, from Nazis to sea monsters. Zawisza called his art "incredible" and "gorgeous", and Immonen a "modern master" whose ability to convey a large amount of story in a small portion of a page Zawisza compared to that of George Pérez. Though Zawisza was not reluctant to note the occasional error, he praised specific visuals, including Immonen and Laura Martin's depiction of Yggdrasil in issue #1, as well as numerous scenes in issue #4, such as the scenes of global chaos, the Odin-Serpent framing sequence and the shots of British Columbia, which he called "chilling".