The 32-year-old, who is mum to three-year-old Buzz and one-year-old Buddy, revealed she was having a “#badmumday” before it had reached 9am.
On World Book Day, Fletcher wrote: “Two major fails before 9am: Dropping a costume-less Buzz off at nursery not knowing they are celebrating.
“This is particularly awful as we totally champion literacy in children and are, as you know, proper authors and stuff.”
Fletcher added: “2. Getting in the car and discovering I had poo all over the sleeve of my jumper.
“I think that bit might be karma for the above.”
The mum-of-two’s post was liked nearly 9,000 times in one day and encouraged other mums and dads to share their own parenting fails.
And for many, forgetting to dress their child up for World Book Day was common.
“I did the exact same thing this morning,” one mum wrote. “I felt bloody awful at nursery. I said ‘I never got the memo’ and the lady said ‘You did’.
“I was like, ‘I’ll change that to sorry I never read it’. Poor little pickle.”
Another person commented: “I did exactly the same with my daughter this morning.
“I was absolutely mortified as I saw all the little Harry Potters and princesses running into pre-school.
“I asked her if she wanted me to go back home and bring her in a costume but she said no... I probably had the poo on my sleeve too actually.”
And another cleverly added: “You must talk about your boys in your ‘Happy Mum’ book so, technically, going as himself is going as someone from a book.”