To 'knock over the fishbowl' is a euphamism for failing a 'girlfriend test', where your girlfriend sets up a test to ensure that you are committed to the relationship.
Alice invited me over to her apartment. Turns out my girlfriend was waiting there... Way to knock over the fishbowl.
When you bang a chick and cum inside of her, then rollover and go to bed, the next morning when you go to take that first piss, you smell that Alfred Fishcock.
The act of ejaculating into one's fishtank...waiting patiently for the fish inside to consume your man chowder, then proceeding to fillet said fish into sushi, serving the meal to an unsuspecting 3rd party (e.g. unfaithful girlfriend, douchey best friend, housemate, etc...)
A: Shanna wouldn't take Tim to taco belllast night, so he totally gave her the Tokyo Fishbowl tonight!