I really wish they'd asked me to do the voice. I'm told (I haven't heard it myself, yet) that they gave me a Minnesota accent, which, as anyone who's heard me speak will tell you, is about as wrong as it gets while still remaining within the American spectrum.
I'll have to watch the whole thing. I'm not a fan of South Park, but I'll make an exception for this one. If you're interested, check out the rerun schedule on the Comedy Central website. It'll be available to watch on the net for free in a month.
I complained about the voice on the South Park forum for the episode...it'll be interesting to see what turns up there.
Update, 3 April: The episode's now available online (make sure to select Canada on Strike). I'm waiting for it to buffer so I can watch.