Just got my facebook sabotaged at lunch and want to sellotape one under the person who done it's chair ready for MOnday morning so when he sits on it it goes off. Can you only get them from Amazon?
What you require is a 'Whoopie Cushion'https://www.amazon.co.uk/s/?ie=UTF8&keywords=whoopie+cushion&tag=mh0a9-21&index=aps&hvadid=3170557057&hvqmt=e&hvbmt=be&hvdev=c&ref=pd_sl_7yldh1qrrm_eHilarity ensues