the act of a rubbish person doing anything rubbishly, or embarassing.
'holy mother of jesus i've only gone and done a shmuel moppet'
'rik waller? shmuel moppet more like!'
'someones done a shmuel moppet' (as the smell of poo poo fills the air)
'have you seen that rubbish olephont costume, the designers a right moppet, its embarassing really, i mean blooming hell its really very crap,