The bikes were built by retired Central Otago farmer John Potts at Bikes 4 Fun and included a ride-on lawnmower bike (a bike with a reel lawn mower for a front wheel), a coalition bike (a tandem where both riders pedal but sit back to back and don't talk to each other) and a water bike (which squirts water up to 15m out the front of the bike seat when you pedal).
The usual unicycles, penny farthings and choppers were also on display.
But many people were attracted to the original 1970 Dragster, with banana seat, sissy bar and T-shift gear box, Mr Potts said.
"They're worth about $1600 - very rare and extremely difficult to find."
Mr Potts said most of the "crazy" bikes were built from old and donated bike parts, and some were designed by school pupils.
The breakfast and bike expo in the Octagon were part of Go By Bike Day and Bike Wise Month (February 1-28)