Alyson Hannigan's middle name is Lee. This is evident from her full name, Alyson Lee Hannigan. She has used her middle name in her professional career, including in her role as Willow Rosenberg on the television series "Buffy the Vampire Slayer" and "Angel".
Unlocking the Talented World of Alyson Hannigan: How Well Do You Know the Phenomenal Actress?