The f-i-l has acquired another bike - or rather, intercepted it between its last owner and the landfill site. The only things wrong with it were a broken crank (!) and a missing pedal, which presumably is still attached to the snapped-off part of the crank somewhere in ATB hell.
Anyway, this uses a BMX/Thompson-type BB with a steel one-piece crank. I was charged with finding replacement components, and got a fairly nice BB and a bog-standard one-piece crank from the Bay. Then we found out that the spare pedals in the garage didn't fit...
One-piece BMX cranks use 1/2", not 9/16" pedals.
Luckily, they're easily available, but what an annoyingly small difference. It's like the 25.4/26.0 handlebar clamp all over again.