Ask HN: Tell me about your internal tools

I know some of this might end up being covered by NDAs, but, I have an obsession with the small unseen tools that are produced by teams to solve a problem.

Some of them are tiny and plug a small niche bug or workflow quirk, others are basically the control room behind a whole complex system.

I like their quirks, and stories they accumulate as well.

So share stories/musing about internal tools you've made, encountered, or read about.

Good or bad :)