On May 26, 2005 (a good two months before the release of Jack's Mannequin's debut album Everything in Transit), Andrew McMahon was forced to cancel all of his upcoming concerts. After a medical examination in connection with a relentless case of laryngitis, McMahon was admitted to a hospital in New York City, where he was diagnosed with acute lymphoblastic leukemia on June 1, 2005. Since the illness was diagnosed in its early stages, McMahon's doctors had high hopes for a full recovery. In the wake of this, many fans started projects to raise money for leukemia awareness. Most notably, the music website AbsolutePunk.net had orange wristbands specially made, reading "I Will Fight" (a line from a song only available on the British version of Something Corporate's North, "Watch The Sky", which McMahon claims to be his favorite song he ever wrote). They sold [over] 6,000 bands, raising [$16,400] which was donated to the Pediatric Cancer Research Foundation (per Andrew's request).
Over the following couple of months, McMahon received various types of treatment, all the while updating his blog, to keep his fans informed on the progress of his condition. August 23, 2005 marked a very significant date for him for two reasons: Firstly, it was the day his album Everything in Transit was released, debuting at #37 of the Billboard 200 with over 22,000 copies scanned within its first week. Secondly, it was the day he received a stem cell transplant, with his sister Katie McMahon serving as the donor. As a thank-you, he and the rest of Something Corporate wrote and recorded a song called "Katie" for her. The song finally was played live at a Jack's Mannequin concert on 7/11/2006 in Cleveland, Ohio. Katie was in attendance for the performance.
On December 2, 2005, McMahon celebrated the 100-day anniversary of his stem cell transplant by playing his first concert in six months – a private invite-only show in a small venue in Los Angeles, California. His first public appearance followed ten days later at "Gimme Shelter '05", an acoustic cancer benefit concert at the Roxy in Los Angeles, California. Following these shows, Maverick Records finally started a promotion campaign for Everything in Transit, including TV appearances by McMahon on Jimmy Kimmel Live, One Tree Hill (in the episode "Just Watch the Fireworks"), Last Call with Carson Daly, Steven's Untitled Rock Show, and The Late Late Show with Craig Ferguson, as well as a second music video for "The Mixed Tape", which hit #1 on VH1's VSpot Top 20 Countdown on June 9, 2006.