There are three Katys in the class

[DandelionDahlia]

Would anyone be able to tell me if this is grammatically correct?

Or should it be "three Katies"?

They all spell their name Katy.

Because it's wrong. "Katy's" would suggest one Katy who owned something.

Katy's book.
Katy's house.
Katy's car etc.

No! 3 ‘Katy’s.
One ’Katy’
Three ‘Katy’s

@SensibleSigma

No. 3 Katy's is incorrect. As I explained. The apostrophe should not be used.

Are you taking the piss here? Please say yes 🙈

@JessicafelloffTheKnappett and @sanityisamyth are you missing the ‘ at the start of Katy?
‘Katy’ is a common name.
There are three ‘Katy’s in the class.

@SensibleSigma

Why are you putting a ' at the start of Katy? Does your name start with a '?

What??? I'm confused, I've no idea what you mean

Perhaps it’s old fashioned now. Titles used to be in ‘ … ‘.

We went to ‘The Old Pig and Whistle’.

Do you know anyone called ‘Katy’?

To be fair, I was at an extremely old fashioned school, 50 years ago. I have noticed people only use ‘…’ convention when they disagree with the word they are emphasising. It used to be used to distinguish between the content of a sentence and the name of something.

Two ‘fish and chips’, please.
‘Fish and Chips’ twice, please.

My examples aren’t great I know, but it was used in that way.

@SensibleSigma but in your examples you haven't said Two 'Fish and chip's so why would it be three 'Katy's?

But it's not a title. It's a name. Using inverted commas around Katy isn't 'old-fashioned', it's just wrong. Especially when you then stick a letter S on the end outside the inverted commas.

@SensibleSigma are you talking about using quotation marks for titles?

www.grammarly.com/blog/punctuation-capitalization/quotation-marks-in-titles/

Names are not titles. 'Katy's has never, and will never, be correct.

Three Katys

It’s a proper noun.

similar to this from a grammar site-

• When talking about a word as a word:

"The" is an example of a definite article in English.

We’re not talking about Katy (a person).
We’re talking about the proper noun ‘Katy’. The name, ‘Katy’.

Anyway, I’m not arguing all night. It was a fun conversation at the start. I’m still amused by ‘Cris’ becoming ‘Crises’.

In the same way as 'Fish and Chips' twice , could we say 'Katy' thrice.

Thanks for explaining what 'Sigma' was talking about... I just didn't get it.

@JessicafelloffTheKnappett I don't think @SensibleSigma gets what they're talking about either ...

I have never heard of a name being put in ' ' . Even my grandparents, who are in their 90s and very 'proper' don't do it.

I thoroughly understand the possessive apostrophe, the grocers’ apostrophe etc.

There are times when a phrase or word is put in quote marks to separate it from the sense of the sentence or to emphasise it.

It’s the usage referenced in these screenshots. You can disagree, it may not be how you’d use it, but I don’t think you can call it wrong- at least not for the reasons you’ve so far used. It’s not a misused possessive. It’s a reference to the word ‘Katy’. Three of them. I could accept your insistence that it should be three ‘Katys’, but not that the inverted comma is entirely unacceptable.

Interestingly this one gets underlined as incorrect. Three ‘Katys’.
This one does not. Three ‘Katy’s. We all know grammar/spellcheck isn’t reliable, though.