[mcv]

Always fun are sentences that sound very similar and are entirely correct in both languages but mean something completely different, like:

He was in the war -- Hij was in de war (he was confused)

A stiff in the brook -- Een stijve in de broek (a boner in the pants)

Those are the two most famous examples I'm familiar with, but I'm sure there are a lot more.

[smcl]

Oh wow, I've encountered a lot of words in English/Czech that are "false friends" but it's too far away gramatically to construct similar sounding entire sentences. That's brilliant you can do it with English and Dutch :)

Also I wonder if there's a connection between trousers being "broek" in Dutch and "breeks" in Scots.

edit: wow ok I should've just went to wikipedia: https://en.wikipedia.org/wiki/Breeks

[ben_w]

At a NATO spy convention, an English spy asks their Estonian, French, Spanish, German, and Bulgarian counterparts if they can see them in the new camouflage they are testing.

"Jah" "Oui" "Sí" "Ja" "Da"

[ben_w]

An ex had the smaller example of incorrectly asking for "un préservatif" when she meant "un préserve".

One of her friends was half of a multi-nationality couple, I think it was French and Irish, and the punchline was their kid, at a beach, yelling, in a strong Irish accent "Look mummy! Phoques!"

[mytailorisrich]

If by "un préserve" they meant a preserve/marmalade then in French that's "une confiture" (or "marmelade" but it's less somewhat rare). I don't think "un préserve" is a word...

[ben_w]

Although I may be misremembering the exact word as I have a GCSE grade D from 23 years ago, her French is much better than mine as she lived in Paris for a few years.

It was certainly something close to what I wrote.