There's very rarely an actual line to stand on ;)

"In line," meanwhile, suggests a line of people, any member of which is, well, "in."

There is a line you stand on, it just isn't drawn explicitly in ink or paint.

If there's no line then you're simply in a sequence of points.

But if we get pedantic we accept this will never satisfy the definition of a geometric line and the Brits were right all along to call them queues.

Yep, I think so. ;)

You're always 'in the' queue (or queuing) though, not 'on' it. So if you must call it a 'line' or a 'line-up', I sympathise most with 'in'.

I somehow knew this was a Seinfeld quote, specifically said by Elaine, before even looking it up.

But turns out it isn’t.

(Edit: Elaine, not Ellen. Thanks for the correction)

The character you are thinking of is named Elaine.