Hader was born in Tulsa, Oklahoma on June 7, 1978. He has two younger sisters, Kara and Katie. His father, also named Bill, managed an air freight company, and his mother was a dance teacher. Hader grew up in Tulsa, but moved to Arizona for college. He attended both Scottsdale Community College and The Art Institute of Phoenix. After college, Hader moved to Los Angeles to pursue comedy. He joined legendary improv comedy group Second City, and did production work on several series for VH1 and MTV, including “The Surreal Life” (2003-06) and “Punk’d” (2007-07). Hader languished in obscurity for several years until he was discovered by “Will and Grace” (1998-2006) actress Megan Mullally, who saw him perform with Los Angeles based comedy troupe “Animals of the Future.” Mullally introduced Hader to “Saturday Night Live” producer Lorne Michaels, who hired him as a featured player on the show in 2005. Hader quickly established himself as a world-class impressionist, and built a sizable repertoire of recurring personalities and characters on the show, including a dead-on Vincent Price and the chain-smoking Italian talk show host Vinny Vedecci.
“SNL” kept Hader in the public eye, but he also made inroads into a film career over the next several years. His first high profile role was in 2006’s “You, Me and Dupree”, a romantic comedy starring Kate Hudson and Owen Wilson. He also made appearances in “Hot Rod”, a stuntman spoof starring his “SNL” castmate Andy Samberg, and Judd Apatow’s surprise smash “Knocked Up”, a subversive rom-com that established Seth Rogan as an unlikely leading man. Hader teamed up with Rogen again in 2007’s “Superbad.” The directorial debut of Greg Mottola, “Superbad” was a high school memoir written by Seth Rogan and Evan Goldberg. Hader co-starred alongside Rogen as a rogue police officer. The movie became an instant cult classic, eventually earning nearly ten times its meager $20 million budget.
The following year, Hader returned for another season of “Saturday Night Live.” He also appeared in a trio of high profile comedies. “Tropic Thunder,” directed by Ben Stiller, was a war-flick spoof starring Stiller, Jack Black, and Robert Downey, Jr., who appeared in black face for most of the film’s running time. Hader appeared as a scurrilous film studio executive. He also had small but memorable roles in “Pineapple Express,” an action-comedy written by and starring frequent Hader collaborator Seth Rogen, and “Forgetting Sarah Marshall,” a breezy romantic comedy starring Jason Segel and Kristin Bell. Both films were produced by comedy juggernaut Judd Apatow, who cast Hader in five of his films. Hader also found the time to act as creative consultant on long-running Comedy Central animated series “South Park” (1997-), and to appear on edgy sketch comedy shows “Human Giant” (2007-) and “Tim and Eric’s Awesome Show, Great Job” (2007-). He would eventually become a producer on “South Park” for its 13th season.