No, it is not fake. Walker's office confirmed it is real.
It's a pretty serious blunder and you have to wonder about the governors call screening operation. Still, there isn't much here that will hurt him.
When the fake Koch suggests planting disruptor's among the protesters, Walker says "we thought about that". This is about the only thing damaging that I could find. It does look pretty amateurish though. Additionally, Walker sort of gives away his strategy to bring the 14 runaway democrats back.
That a major Republican governor could be so easily punked is kinda sad. The media will have a field day with this and it will end up benefiting the unions for at least awhile. Fortunately, there really isn't anything big here and Walker sounds like the same calm, rational and reasonable person that he is in his press conferences.
I read the exchange about “disruptors” meaning counter-protestors. It’s nothing, and in the end Walker opts vocally for keeping the peace above countering the din.