How I Met Your Mother is noted for the large number of actors featured in it who have also worked with renowned fantasy/sci-fi writer/director/producer Joss Whedon. Co-creator Craig Thomas' wife, on whom Lily is based was a "Buffy the Vampire Slayer" fan and suggested Alyson Hannigan to play the character. This started a trend with actors who had previously appeared in Whedon productions guesting on the show or in Neil Patrick Harris and Cobie Smulders cases would star in Whedon productions after appearing on HIMYM. In the case of Cobie Smulders, she was recommended to Whedon by HIMYM co-stars Alyson Hannigan and Neil Patrick Harris.