We Changed It Once And Everything Died

You know that Excel spreadsheet running your company's entire financial infrastructure? The one with macros written by Karen from accounting who retired in 2003? Yeah, nobody's touching that. It's been copied, pasted, and frankensteined across departments for decades. The formulas reference cells that reference other sheets that reference a SharePoint folder that may or may not exist anymore. Documentation? What documentation. Comments? Just "//fixed - don't touch." The business logic is buried somewhere between columns AF and BQ, and the only person who understood it left the company during the Bush administration. You could rewrite it in a proper system with tests and version control, but why risk nuclear winter when the ancient artifact still technically works?