So this is not as bad as some of the other stories I've seen, but I'll bite.
It was an old .NET Framework MVC app. Some internal product management system or something. There was a need to do a PDF export in one of the use cases, so someone implemented it. It wasn't a good implementation: one big controller, mixing UI and business logic, etc. However, it basically came down to a single private method in a specific controller for a page.
Now time passes and lo and behold, we need a PDF export in another page for a different use case. "No problem," - same dev, probably - "I already solved this problem. I'll just reuse the PFD generation logic."
Now, any sane person would probably try to refactor the code responsible for PDF stuff into a separate service (class) and reuse it. A less sane, but somewhat, acceptable approach would have been to just copy paste the thing into another controller and call it a day.
Ha! No no no no no no… Copy pasting is bad, code should be reused…
The end solution: REFLECTION. So the dev decided that the easiest way to make it work was to: 1) use reflection to inject one controller into another; 2) then use reflection again to get access and call that private method for PDF rendering into a stream.
Fortunately I didn't have to fix that fragile mess. But I did my fair share of DevExpress corpse hacking and horrible angular "server side rendering" workarounds.