Can be similar to the police interrogation method called good cop / bad cop.
Can be sexual with one in the poot and one in the shute.
In any case, both actors supplement or intensify the effect of the other while remaining individually distinct and somewhat opposite in mannerism.
GOOD FUNG FU: "Snatch the pebble, grasshoppa."
BAD KUNG FU: "No tickee, no washee."