Bonnie Lancaster, nine, of Orchard Road, Brentford, went out for some last-minute Halloween party supplies with her mum Portland Lancaster, to the Morrisons on the High Street and decided to test run her home-made trick or treat costume.
She was met by horrified looks which quickly turned into plenty of laughter as she walked around the supermarket, and it was similar on the bus journey home.
The pair who made the costume over the half-term break were thrilled with the reaction which included people wanting to pose for a picture with the headless zombie, a lady who ran back into the supermarket from the car park to pop some sweets into the box, and some screams of shock.
Mrs Lancaster said: "We got a hilarious reaction.
"The first reaction was of shock and a horror and then people laughed.
"Everyone was coming up saying "you got me" or laughing and pointing.
"On the E2 bus from Morrisons people would scream as they got on the bus and then they would laugh. Even the driver had a giggle.
"It got a lot of people laughing which was such a nice thing."
The body was filled with bubble wrap and kitted out in a shirt from Oxfam, gloves from Primark also stuffed, and a metal coat hooked to the box which was painted in fake blood spatters.
Last year the mother-daughter made a mad scientist costume and will be looking to up their game for next year.