[2][3][4] Masterson was raised in Los Angeles and began his career at the age of six when he appeared in a Count Chocula / Franken Berry television commercial, directed by Bill Melendez.
Masterson started working with Ryan Stiles and Drew Carey upon returning to Los Angeles, performing live improvisational comedy as a part of "The Improv All Stars".
Masterson created and co-wrote the web show "Home Purchasing Club" (HPC) for VH1/Spike,[5] which ran for two seasons and featured Kristen Wiig, Jeff Garlin, Diedrich Bader, and David Koechner.
Masterson created, wrote and directed "Republicrats" for MSN (Microsoft), portraying a former Fresno TV weatherman who decides to run for President of the United States against John McCain and Barack Obama.
Republicrats was reviewed by The Wall Street Journal, The Hollywood Reporter and TV Week as a Top Web Show of 2008.