The best English mistake I’ve come across so far: the nightbox.
Vincent: “So, class, what did you do this weekend?”
Student: “Zees weekend, I go to zee nightbox. I have drink lot.”
Nightbox is simply a too-literal (yet somehow wonderful) translation of la boîte de nuit (nightclub).
Since, according to their accounts, my students’ lives are primarily occupied by two activities — (1) drinking and (2) sleeping — if I can get them to talk correctly about those things, I’ll have to consider it a success.