Alternate lines for the flies (Fly 2 would need it’s upper left arm propped on it’s waist instead of it’s current position):

Fly 1:  I wish I knew who was telling the truth.
Fly 2:  They both are.

Fly 1:  I wish I knew who was telling the truth.
Fly 2:  Oh come on.  You know which one produces the most shit.