'You _____(joke),'I replied.'I ____(not know)anyone who does.'

'You _____(joke),'I replied.'I ____(not know)anyone who does.'

you are joking (==you must be joking)
don't know

are joking ;don't know

...

1.are joking
2.don't know

you're joking
don't know

are joking ;didn't know