Looking on the internet deeply has found these results:

That only happens is the most popular phrase on the web.

That only happen 1895,000 results on the web	That only happens 11,440,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	For a transit to happen, it has to overtake us, but that only happens once every 1.6 years. That only happens with dogs. That only happens if the bones have been cleaned and treated. But then I realised that passion is something that only happens to other people. That only happens in a second or third meeting. That only happens if somebody high up on the inside's being paid off. That only happens when you're a little high. I know that only happens in movies, but I do.

That only happen

1895,000 results on the web

That only happens

11,440,000 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

For a transit to happen, it has to overtake us, but that only happens once every 1.6 years.
That only happens with dogs.
That only happens if the bones have been cleaned and treated.
But then I realised that passion is something that only happens to other people.
That only happens in a second or third meeting.
That only happens if somebody high up on the inside's being paid off.
That only happens when you're a little high.
I know that only happens in movies, but I do.