Saw this today at work on the copy machine as I was frantically trying to get papers run off for 1st period before the bell rang!
I knew it had to be a prank because for that type of new feature to be installed we would have had to get a new copier. The technology would just be too advanced for what we have.
I did find it funny, but would have felt bad if I saw someone trying to use the "new" feature. So I showed to the people I saw. So, sorry if I ruined your joke. It was a good one and reminds me of one that I did at a different job.
I put a piece of paper on the copier that said, "Do Not Remove This Paper!" It stayed there for a few days. Someone finally threw it away as they proclaimed that it was silly for it to be there. It was a nice little private joke. :)
I wish I could take credit for the voice activated printer prank, but at least I can say that I didn't fall for it! It does make me want to try something. Nothing bad, but something. I will have to see what I can come up with. They always say to watch out for the quiet ones...