Most parents know there tends to be one or two ring-ins at kids birthday parties - it's bad form but hardly the child's fault.
Now one parent has retaliated. The fed up UK mum recently made gatecrashers at her child's party eat discarded food from a bin.
The whole shocking story was recounted on Mumsnet by a parent in the local community who heard about the furore the mum's actions stirred up. The post caused outrage among commenters, with a few leaping to party mum's defence.
The poster begins writing that uninvited siblings had become quite the problem at local children's birthday parties.
"There was a whole-class party at a leisure centre last weekend at which the hosting mum had done little lunch boxes for each child with the usual - rolls, fairy cakes, fruit, veg sticks, crisps etc. There were unfortunately several uninvited siblings dumped by their parents at the start of the party," she wrote.
After detailing how she herself would deal with unwelcome interlopers (by stating on the invite that only invited kids could come), she then revealed the party mum's horrendous strategy.
Readers, we reveal to you, the "yuck bin."
"This mum had brought a little bin with a sign on it saying 'Yuck Bin' with a vomiting emoji, which she passed around for all the children to put the items they didn't like from their food boxes. Then the uninvited siblings were allowed to take food from the Yuck Bin."
Apparently it caused a "bit of a scene" once one of the mums of the uninvited kids heard about it - though she can hardly be on her high horse when guilty of dumping an extra child at the party.
The poster wrote that although she wasn't there, she heard that, "... one of the mothers of the additional children flipped out at the end of the party when she was told by her child about how he was fed."
And while she could see the point the mum was making, she thought her "... way of dealing with it was horrible," and that, "...nobody has behaved very well here."
The thread has attracted more than 600 responses to date.
"That is an atrocious way to treat kids. Any shaming should be aimed at the parents," wrote one person.
Another said, "Giving them food from a 'yuck bin' is so demeaning to the children. I'm actually appalled by it."
"You should never punish a child for what their parents have done. The host should have refused siblings at the door like the adult she is and made it clear she can't/ won't accommodate siblings," wrote another.
One responder saw it as a "good solution" if the food hasn't been touched.
"If the unwanted food was untouched this is a good solution. I imagine most kids would think the vomiting emoji was funny. It is so rude to dump your kids at a party they aren't invited to. I can't imagine accommodating it. Don't you just say no? Politely of course."
Someone else said the kids wouldn't be affected.
"It was excessive but sometimes excessive is the only way to get things done. Maybe the rude parents leaving uninvited kids will think again next time. The children won't be scarred by this."
This one disagreed.
"My kids would absolutely care about being fed cast off items from a bin."
And on the last page of comments, when every angle has been explored to death, and finally there's this.
"I see no issue. I think it's pretty yuck turning up with uninvited children."