Find a movie none of you has seen before, spoken in a language none of you knows. If it has subtitles in your language, turn them off. Each time when a character in the movie speaks, somebody improvises a "translation" of what they're saying. Optionally, each character in the movie may be "adopted" by the first person to translate them, who then translates all of their lines from that point on. Or not, in which case all characters remain free-for-all. See for how long you can keep the story consistent.
To make things more interesting, you could decide to change the genre of the movie. For instance, if you know that it's a romantic comedy, you could decide beforehand that it's really a sci-fi drama, or vice versa.