The Tooniverse had a full crossover this week, not just the 'Family Guy' immersion into Earth Prime-Time on 'The Late Show'.
(Actually, it happened a few weeks back, as it aired in Ireland first.)
The Green Arrow's sidekick Speedy (now known as "Arsenal" in the DC comic book universe) showed up to give his mentor and a lot of the non-super-powered heroes in the 'Justice League Unlimited' a hand against a demented military officer who was threatening to go all hulkish on Metropolis.
Speedy has been a recurring team-mate in 'The Teen Titans', and so that makes a crossover between 'The Teen Titans' and 'Justice League Unlimited'.
Some might argue the point because the artistic rendering of the two shows is so radically different. But I think the denizens of the Tooniverse are "real"; it's just our perception of their depictions vary from those characters we see in the live-action TV dimensions.
Besides, as Thom pointed out in his coverage of this crossover in his "Crossovers & Spinoffs" page, (Link to the Left), both portrayals of Speedy were voiced by Mike Erwin. I have no bias towards voice actors; I think they do a lot of work in creating a character and stamping it with their imprint.
So if Mike Erwin plays Speedy on both shows, than that's what marks him as the same Speedy in both shows, not his artistic rendering.
Nuff said! (Oops! Wrong comic book company. Sorry, True Believers! Damn!)