A childhood belief about fear of

it was like two weeks before we sold our house. i was five and my brother was three. we had a problem with our upstairs toilet. it would work fine except for the fact that an air bubble would form and it would make a huge POP. so one morning me and my mom and i were in the living room and my brother woke up and used the bathroom. we hear the flush and the POP. all of a sudden, we hear my brother scream AAHHH THERE'S A MONSTER IN THE POTTY!!!!! (he apparently forgot the problem my dad had explained the other night) so he tries to come downstairs with my mom and me where we are watching . my mom was afraid that one of her kids would end up being a sleep walker and sense our bedrooms were on the top floor she had this saftey gate at the top of the stairs. it was really hard to get open. well my brother is so afraid that he forgets how to open the gate so he flings himself over it and he rolls head over heels doing somersaults down the stairs. he wouldnt use the upstairs toilet untill we mooved into our new house in fear of the monster in the potty.