Thomas made his big screen debut as Young Flaco in Nick Gomez's hard-hitting New York City-set drug fable "illtown" (1996). He would later appear in Noah Baumbach's "Mr. Jealousy" (1998, also set in New York) before landing a supporting role as geeky Arnie in the toothless teen-aimed thriller "The Rage: Carrie 2" (1999).
Thomas reached his widest audience to date with a featured role in the summer hit teen sex comedy "American Pie", playing Finch, a young suburban Michigan resident who compensates for his pubescent awkwardness by aspiring to a sophisticated continental lifestyle, including sipping mochaccinos, riding a Vespa and peppering his droll pronouncements with Latin phrases. The inclusion of Finch's obsessive distaste for the school washrooms set the scene for the film's requisite bathroom humor, pulled off admirably by Thomas, who balanced its questionable taste with a natural flair for physical comedy, while maintaining the strange dignity and disarming charm of his oddball character. Finch comes out a winner in the film's central sexual quest, losing his virginity to a well-preserved older woman who appreciates the young man's physical youth and mental maturity. The actor reprised the role for the sequels "American Pie 2" (2001) and "American Wedding" (2003).
Thomas appeared as a youth in several other films, ranging from the dramatic (writer-director James Toback's "Black and White" in 2000) to the comedic (with Tom Green in "Freddy Got Fingered" in 2001) to the experimental ("Stolen Summer" in 2002, the first film made by Miramax in conjunction with HBO's "Project Greenlight" documentary series). The actor also had the leading roles in a pair of shortlived TV series, the dramedy "Brutally Normal" (2000) and sit-com "Off Centre" (2001-2003), co-created by "American Pie" scribes Paul and Chris Weitz.