Ask HN: Stories of people joining a company just to fix an issue then leaving?

While obviously rare I think I've read two cases of this happening before, one was to do with xcode iirc and the other was probably something to with apple as well.

I chanced on this tweet[1] (which is fake) but it's a pretty interesting occurrence. Please share any stories below that you know of.

[1] - https://twitter.com/swaglord__420/status/1377051721655066629