I think the best was when, in answer to my boyfriend's father's question about how long i'd lived in chester (in french!) i answered "10 minutes" much to the amusement of everyone at the table! (bit of a misunderstanding of the questions there!)

And then on my second visit I wanted to thank my boyfriend's mum for washing my clothes so asked my boyfriend how to say it, practiced it in my head then said "Merci d'avoir laver mes amis"!! Not my fault 'habis' and 'amis' sound so similar!!