[3] The following year, he was also considered for the role of Harry Potter due to his Irish heritage and Scottish ancestry, as well as his previous work with director Chris Columbus on Stepmom,[6] but Daniel Radcliffe ultimately won the role, due to J. K. Rowling's insistence that the part should go to a British actor.

[7] Aiken went on to play intelligent 12-year-old orphan Klaus Baudelaire in Lemony Snicket's A Series of Unfortunate Events (2004).

[11] In 2014, he played the title role in Ned Rifle, the third film in a trilogy that began with Henry Fool and continued with Fay Grim (2006).

[12] In 2020, he co-starred The Bloodhound, a mystery film inspired by the Edgar Allan Poe short story "The Fall of the House of Usher.

"[13] In 2021, he portrayed an electronic musician who suffering a series of nightmares with bizarre and mysterious appearances in Bashira, directed by Nickson Fong.