Thread:AHI-3000/@comment-28007502-20170516003702

Hi there. About the X-9/X-49 article... The whole "X-9" thing seems to come from a typo on fan forums (notably a talkback thread on ToonZone) that propagated back in the mid 2000s. All official sources -- press releases, episode credits, Annie Awards listings, Turner's listing for the episode, and the place where you can purchase it on YouTube -- use X-49 or X49.

This feels a bit like when P2P file-sharing misattributes a song to a well-known artist. It just gets passed around as "common knowledge," despite being based on a mistake. 