I'm fascinated by doubled words in ordinary¹ English sentences, such as:
…the company I worked for for ten years…
…I noticed that that man is tall…
…they had had their dinner…
…I do do that…
The words aren't technically duplicated since they have different functions, but it's still cool. I wonder if anyone's catalogued all the words this naturally² happens with.
1. Not sentences constructed to duplicate a word.
2. Words in quotes not allowed (…this "this" is in the wrong font… etc)