In 2007 Immonen began working for Marvel Comics writing a Hellcat story, with Stuart providing the art, for the first four issues of Marvel Comics Presents.[2][3] This was followed in 2008 by a five issue Patsy Walker: Hellcat mini-series,[4] this time with artist David Lafuente.[5]
Kathryn and Stuart Immonen have been creating various webcomics alongside their print work for Marvel Comics. Their first webcomic was Never as Bad as You Think, which was published by Boom! Studios in December 2008. The webcomic was followed by Moving Pictures, which saw a print publication by Top Shelf Productions in April 2010. The latter webcomic took on a darker tone than the humorous Never as Bad as You Think, taking place in 1940s France during World War II and starring a Nazi protagonist.[9]The A.V. Club described Moving Pictures as "illustrative of what a major writing talent Immonen really is."[10]
Immonen and artist Tonči Zonjić collaborated on Marvel's mini-series Heralds, featuring an all-female cast of main characters.[11][12]
January 2011 saw the release of Marvel Comics new four-part mini-series Wolverine and Jubilee, with artist Phil Noto. In 2012, she took over the Journey into Mystery title with issue #646, transitioning from Loki to Sif as the main character.
AVX: VS #1, "The Thing vs. Namor the Sub-Mariner", #6, "Science Battle!" (with Stuart Immonen, April, October 2012) collected in Avengers vs. X-Men: VS (tpb, 160 pages, 2013, ISBN0-7851-6520-7)
Avengers Annual vol. 5 #1, "It's the most loneliest time of the year!" (with David Lafuente, December 2013) collected in Avengers: Revelations (tpb, 136 pages, 2015, ISBN0-7851-9340-5)
Spider-Verse #2, "Anansi: A Spider in Sheep's Clothing" (with David Lafuente, January 2015) collected in Spider-Verse (hc, 648 pages, 2015, ISBN0-7851-9035-X)