Dad: Ok son, if you fail this test, you're no longer my child, ok?
Son: Ok dad.
AFTER TEST
Dad: Hey son, how'd the test go?
Son: Son?
The Test Result
Categories
Explanation
Experiment
Explain Bear
Listen up, buddy. You are the kinda person that needs things spelled out, so here it is. The dad made a conditional statement: if you fail this test, you're no longer my child. The son, after the test, responds with 'Son?' which implies he doesn't consider himself the dad's son anymore because he failed the test, therefore the statement was true. The humor comes from the literal interpretation of the dad's hyperbolic statement.