The plan was to tell his partner he has been seeing someone else for a while. He then planned to take things further by telling her the other girl is pregnant. Things started out on plan when his partner entered the room and he sat her down. He then started his rehearsed speech and received the expected reaction when his girlfriend went crazy hitting him before running out of the room.
What he didn’t know was that his girlfriend actually knew what was happening as his friend had already told her about the prank. She then got him back BIG TIME.
This is why you never mess with a woman.