Alt Bike Culture - Bicycle with unicycle front wheel?

I went to the circus last night and among the performances was a guy with a trick bicycle that the fork, seatpost, and cranks came off and became a freestanding unicycle. I imagine this was custom built but it got me thinking about how if you turned the forks of a regular bicycle into forks that could hold a unicycle hub/wheel you could build a ridiculous tandem bike where the "stoker" at on the handlebars and pedaled the front wheel.

Has anyone ever attempted this?

I know a unicycle hub won't fit a standard fork and a standard unicycle won't work as a fork but it seems like you could probably chop one and weld it to the other to make a [quazi]functional machine.

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I can not put the pedals on, but is this what you have in mind...have not seen it done but sounds like you could, as has been said, weld something together.
My thought has been to make a small penny-farthing with the Unicycle that I have...one of these days.

The unicycle would be geared 1:1, whereas a normal bicycle is geared 2:1 or 3:1 or so, so it would be pretty irritating to ride. It would also take some coordination as to who moved what to maintain balance.

My idea was to do that so that you could have a single-speed bike, but when you come to a steep hill, hop on the unicycle cranks and pedal on up.

They have built tandem unicycles before.