An alien of a species identified as the Graske appeared in "Whatever Happened To Sarah Jane?", the penultimate episode of the first season of 'The Sarah Jane Adventures'. Played by Jimmy Vee, the Graske was not encumbered with a name, and so it could be that he was the same Graske as was seen in the interactive adventure "Attack Of The Graske". This aired on the same night as "The Christmas Invasion" back in 2005.
So there's proof that online content - on a limited basis, I hope! - will have to be accepted into Toobworld proper, as is the case with several movies like the 1966 'Batman', 'Maverick', and the 'Star Trek' franchise.
But it wasn't the first time that a character created for an online source later appeared in a TV series. That honor may belong to Lt. Walter Neal, who worked 'Homicide: Second Shift' in Baltimore. We first saw him online in February of 1997, and then a year later he showed up in a January episode of 'Homicide: Life On The Street'. (Both versions of 'Homicide' shared a three part crossover, "Homicide.com" with the bracketing episodes done online.)
Does anybody know of an online character who crossed over into Toobworld proper before Lt. Neal and his team? Let me know!