The Radio 1 DJ, who is expecting a baby with boyfriend Jesse Wood, explained on her show today (November 1) how she tried to "get into the spirit" of the spooky occasion, but was left stunned when things "got uglier" later in the night.
"At about 8.30pm, the doorbell went for the last time and I answered; there were three little kids there," she told listeners.
"The first kid said to me, 'Have you got any money?' and I said, 'No, you can have a sweet'. The oldest kid took a big handful of sweets and walked back down the path.
"As the other two little kids took sweets for themselves, the older kid shouts, 'I don't like these ones' and starts throwing toffees at my face."
She continued: "Usually I'm quite feisty and would go, 'Excuse me, get out of here', but I was so shocked I just stood there looking at him getting pelted with toffees. This morning there was a debris of sweets everywhere in my front garden."
Cotton spoke about becoming calmer during her pregnancy in a September interview, commenting: "I'm trying to take it easy for the first time ever.
"Normally I live at a hundred miles an hour, so I never get to see any of my friends. This year I'm not doing loads. Instead I'm going to see all my friends, family and boyfriend and just try and have a bit more of a life."