Language learner mistakes:
My own contribution to this genre happened in 2004-ish, when I went to a camera store and told the guy behind the counter that I needed 'eine Speichelkarte'.*
* As the video shows, explaining the mistake is more droll than funny, but here goes: I wanted a memory card (Speicherkarte) but instead asked repeatedly for a 'saliva card' (Speichelkarte). The guy behind the counter, richly amused, asked me how many megabytes of saliva I needed to store.