User blog comment:Coolbloo12/Beastboy joining YJ?/@comment-108.75.17.27-20120318164927/@comment-1038387-20120413190500

There's a myriad of teen sidekick-y characters to choose from in the DC Universe. It would be pretty unimaginitive to have the same guys as the last show. Four of which weren't even sidekicks, and would therefore not even fit in the premise of Young Justice.

A guest spot might work, like we saw with Garfield, but it was Garfield like he was in the comics, not in Teen Titans. Cyborg/Victor Stone could have a similar pre-cape appearance, though with the characterization of Mal Duncan, that would be redundant - why introduce a new character when another already more or less fits the description?

Having all three (plus Garfield) them all show up at once would serve even less purpose. Unlike previous DC shows, but not unlike previous Greg Weisman shows, Young Justice is a pretty continuity heavy show, where just about everything happens for a reason. In a young universe (even for season two) there would be no reason for those three specific heroes to appear together.

As for the greatest thing we would ever see... that's open to debate. I think, from a story telling point of view, it would totally wreck the series.