Editing Alyson Hannigan (section)

=== 1986–2004: Career beginnings and breakthrough ===
Hannigan's first major film role was in ''[[My Stepmother Is an Alien]]'', a science-fiction comedy released in 1988; one of her co-stars in the film was actor [[Seth Green]], who later joined her in the regular cast of ''[[Buffy the Vampire Slayer]]'' as her on-screen boyfriend.<ref name=CBS/> In 1989, her first regular role on a television series came when she was cast in the short-lived [[American Broadcasting Company|ABC]] sitcom ''[[Free Spirit (TV series)|Free Spirit]]''. 
[[File:Alyson Hannigan at HIMYM.jpg|alt=Hannigan smiling|thumb|260x260px|Hannigan at a celebration of the 100th episode of ''[[How I Met Your Mother]]'' at the Paley Centre, 2010.]]
In 1997, Hannigan was cast to play [[Willow Rosenberg]], [[Buffy Summers]]' best friend, on the [[supernatural]] [[Television show|television series]] ''[[Buffy the Vampire Slayer]]''.<ref name=":3">{{cite web |title=Where Are They Now? Buffy the Vampire Slayer |work=[[People (American magazine)|People]] |url=http://www.people.com/people/article/0,,20170817,00.html |date=December 3, 2007 |access-date=June 12, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20140202164519/http://www.people.com/people/article/0,,20170817,00.html |archive-date=February 2, 2014}}</ref> The show became a success, and Hannigan gained recognition, subsequently appearing in several films aimed at teenage audiences, including ''[[Boys and Girls (2000 film)|Boys and Girls]]'' (2000).<ref name="CBS" /> She had a supporting role as [[Michelle Flaherty]] in the [[comedy film]] ''[[American Pie (film)|American Pie]]'' (1999), and appeared in a much larger role in its sequels ''[[American Pie 2]]'' (2001) and ''[[American Wedding]]'' (2003).<ref>{{Cite web |title=American Pie Cast Reunites After 20 Years! Watch Them Discuss the Infamous Band Camp Line |url=https://people.com/movies/american-pie-cast-reminisces-one-time-at-band-camp/ |access-date=2024-06-22 |website=Peoplemag |language=en}}</ref> In 2017, ''[[Forbes]]'' reported that the ''[[American Pie (film series)|American Pie]]'' films have grossed $989.5 million at the worldwide box office, and became a [[Popular culture|pop culture]] [[phenomenon]].<ref>{{Cite web |last=Thompson |first=Simon |title=Seann William Scott Talks 'Goon' Sequel, More 'American Pie' And 'Dude, Where's My Car?' |url=https://www.forbes.com/sites/simonthompson/2017/08/28/seann-william-scott-talks-goon-sequel-stifler-more-american-pie-and-dude-wheres-my-car/ |access-date=2024-06-26 |website=Forbes |language=en}}</ref><ref>{{Cite web |last=Leigh |first=Clarissa |date=2023-02-22 |title=Why the American Pie Movies Were So Popular and Successful |url=https://movieweb.com/american-pie-why-so-popular-and-successful/ |access-date=2024-06-26 |website=MovieWeb |language=en}}</ref>

She also had a recurring guest spot on the ''Buffy the Vampire Slayer'' [[Spin-off (media)|spin-off]], ''[[Angel (1999 TV series)|Angel]]'', reprising her role of Willow. In early 2004, Hannigan made her [[West End of London|West End]] debut, starring in a stage adaptation of ''[[When Harry Met Sally...]]'' at the [[Haymarket Theatre|Theatre Royal Haymarket]], opposite [[Luke Perry]].<ref>{{cite web |url=http://www.britishtheatreguide.info/reviews/harrysally-rev.htm |title=When Harry Met Sally, Review by Philip Fisher (2004) |publisher=British Theatre Guide |access-date=April 18, 2010 |archive-date=October 24, 2023 |archive-url=https://web.archive.org/web/20231024213823/https://www.britishtheatreguide.info/reviews/harrysally-rev.htm |url-status=live }}</ref>