The intern was tasked with a large-scale refactoring of some modules which the senior devs estimated would take months of work to complete. After shadowing a senior dev to get an idea of the work involved, they realized the dev was literally string replacing a lot of the code, hence why the estimate was ridiculously long. The intern instead loaded the project into IntelliJ and used the built-in refactoring tools to get the task done in a couple days. This caused a bit of an internal shit-storm with the product owners because the intern made the devs "look bad".