Who drew on this banana? Sandra

"Who drew on this banana?"  Charlie looked up from his dish of breakfast cereal at his mother, who was standing accusingly in front of him. Waving a banana in her hand that was covered with strange symbols written in red felt pen..
"It wasn't me." Charlie muttered, "it must have been Amy." He glanced over to where his baby sister was
playing with her dolls.  It was not that Charlie wanted to get Amy into trouble but at two years old Amy, it seemed to Charlie could get away with anything even drawing on the walls.
"Charlie," his mother said in an exasperated tone. "Amy can barely hold a pen she could never draw those
patterns. If you cannot tell the truth there will be no computer games tonight after school."
"But Mum," Charlie protested. His mother gave him a hard stare and he knew it was pointless to continue
protesting.  He got up sulkily, kicking his chair back under the table.
"Charlie," his mother shouted.
Charlie put his hands over his ears. he was fed up with always getting the blame for everything in this house.
Every other minute his mother seemed to be shouting at him "Charlie, Charlie, CHARLIE! The worst of it was that Charlie knew very well who was responsible for all the mysterious goings on in the house. The awful thing was if he told his mother she would never believe him.
From inside his hiding place Gollo grinned a toothless grin and bit on his long green fingers to stop himself laughing out loud.  Gollo liked nothing more than causing trouble and mischief and Charlie was an easy target.
As Charlie walked through the hall his nose picked up on a familiar smell.  A strange sour smell a bit like strawberry yogurt that has gone off,  mixed with the smell of his football socks after football practise.  the odd thing was Charlie was the only one who could smell it!
'Gollo' he thought. He must be very close, the smell was very strong.  Charlie tipped out the contents of his school bag, remembering the time that Gollo had hidden in his bag and caused him endless trouble at school. His pencil case, reading book and favourite marbles clattered down on to the floor.
"Charlie." His mother shouted from the kitchen.
Gollo could not stifle a giggle and Charlie looked in the direction the noise had seemed to originate from.  The boot cupboard. One of Charlies wellingtons was shaking on the shelf. 'Got him' Charlie thought. He crept closer, grabbed the boot and putting his hand over the top to stop Gollo escaping, he ran up the stairs to his room.  Banging the door shut behind him. 
Charlie tipped Gollo unceremoniously out onto his bed. Gollo landed face down on Charlie's duvet leaving a large  stain of green snot from his constantly dripping nose.  'Oh no', thought  Charlie, 'Mum will go nuts when she sees that'.
Gollo sat up and blinked up at him with his small red eyes. "Well", Charlie asked, "Why did you draw on the banana?