Green filmed scenes for the 1992 Buffy the Vampire Slayer movie, but they were eventually cut out. However, Green can still be seen on the home video box. Along with Chi Muoi Lo, he is one of only two actors to appear in both the original film and the television series.
In the late 90s/early 2000s, Green earned greater acclaim after appearing as Dr. Evil's son Scott in the Austin Powers trilogy.
Green also voices the character of Chris Griffin on the animated comedy series Family Guy and is one of the creators and producers behind the stop-motion animation comedy series Robot Chicken (which has been known to parody the Mutant Enemy logo).
Green was also a guest-star on the show Heroes alongside Clea Duvall (Marcie Ross), Carlease Burke (Winslow), Nicole Bilderback (Unidentified Cordette), Dominic Keating (Blair), Elisabeth Röhm (Kate Lockley), Leonard Roberts (Forrest Gates), Lawrence Turner (Hank), Colby French (Tay), Chanie Costello (Inga), Julie Costello (Ilsa), Todd Stashwick (Vocah/M'Fashnik Demon), Edwin Hodge (Keenan), Matt North (Stephen Kramer), Cory Hardrict (Ray), Franc Ross (Razor), Jonathan Goldstein (Mike), Christopher May (Unidentified male customer), Steve Tom (Stephen Mills), Mark Harelik (Kurskov), Kevin Christy (Josh), Riki Lindhomme (Cheryl), Dania Ramirez (Caridad), Bart McCarthy (Nostroyev), Mark Colson (Izzerial) and Irina Maleeva (Goran Maid).
One of his young roles is in the Stephen King tv-movie adaptation Stephen King's IT playing the young Richie Tozier. Ironically this character has a fear of werewolves. He would later play a werewolf in Buffy.