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 a teacher searches for the definition of a random string of words during a health class. It must sound like something sexual related but really isn't. You can replace "pepsi" with "soda", "coke", or any other drink.
Student: "What does it meant to knock over the pepsi?"
Teacher (searches it up): "I don't know." (Finds urban dictionary result) "You got me."
When someone from another room hears you knock over an object and thinks you did, but in reality you weren't even close to object, which fell on it's own for no apparent reason, so you blame a ghost.
Kenny: What was that noise?
Aaron: oh, I ghost-knocked-over grandma's picture thing.
Kenny: Just fell on it's own?
Aaron: Yeah, it was a ghost-knock-over
Kenny: you doth protest too much