Halloween may still be more than a week away, but it looks like we already have a very strong contender for costume of the year.
Explaining how she created the costume in the Extreme Couponing and Bargains UK page on Facebook, the 25-year-old said: "Primark tights £2, Amazon wig and costume £19.
"Leftover helium and balloon from birthday party and last year's face paint."
The post has since received more than 28,000 likes and countless comments - most of which were from people who thought the get-up was a little bit too spooky if anything.
One person said: "Scary! Amazing but really gives me the creeps."
Another said: "This is great... I mean, I wouldn't be opening my door on Halloween night.
"Officially the creepiest child I have seen. Fab job!"
A third added: "It's amazing! But if that child knocked on my door trick-or-treating, my two-year-old wouldn't sleep for a week... Or me either!"
Miss Harrison, who works as a warehouse operative, said her son loved the costume too.
Speaking to LADbible, she said: "My son likes scary films and watched the IT movie and wanted to dress up as him on Halloween.
"It's a bit early for Halloween but he wanted to try it on as soon as it arrived so I thought I'd get a quick snap of him in his costume, and yes, he will be wearing it again on the day.
"My son loves it and says it's his favourite costume he's had."
But while the youngster - and loads of people on the Facebook page - thoroughly approve of the costume, not everyone thinks dressing your child as Pennywise is very wise.
Miss Harrison said: "I've had mixed reactions, good and bad. Most people say how amazing he looks but you get the odd person saying he shouldn't know who [Pennywise] is at his age."
Conversely, if you're a little too old to be dressing up and going out trick-or-treating this year, then you could always stay in with Morrisons' Trick or Treat Roulette pizza.
The pizza contains ghost chillies - which measure more than one million units on the Scoville heat scale - hidden in random slices. Look no further if you're after an unpredictably and unbelievably spicy pizza this Halloween.