It's common knowledge that the "Far From Home" episode of the "Justice League Unlimited" series was supposed to be a back-door pilot for a proposed Legion series.
Well, common knowledge is wrong in this case.
Via ToonZone, here's an excerpt from a Feb. 2009 interview with Bruce Timm, animator and producer:
Q: I understand the episode "Far from Home" from Justice League was supposed to be some kind of a pilot for a Legion of Superheroes show?
TIMM: Not really. No...
Q: So the fanboys on the Internet have no idea what they're talking about?
TIMM: Imagine how THAT could happen! (laughs) No, we just wanted to do a Legion of Superheroes story, and again, going from the comics where Supergirl and Brainiac had a romance, we thought, "Oh, that would be an interesting thing to do with Supergirl that we hadn't done before." We hadn't really shown her as getting into more adult issues of romance and stuff, so it just seemed kind of like a fun thing to do. But it wasn't ever intended to be a backdoor pilot, no.