Based on the activity "Puro Cuento" in Técnicas Participativas Para la Educación Popular Vol. 1.
Joker gives pairs of participants 5 minutes to choose a short text -- about one-half to one page long. (The text needs to be available to all. A passage from a textbook, a handout prepared ahead of time, a webpage everyone can find on their phones...)
Joker then gives pairs 20 minutes to prepare a lecture of lies, in which they take facts or information or opinions from the text and reverse them, writing a simple lecture with mostly lies (it is good to leave a few true statements, to keep people on their toes).
Joker then calls on pairs to present their lectures. The other teams listen and call "That's not true!" The first team to call out and prove that the lecture point is false, using the text, gets the point.
OR, lecturers complete their presentations, then teams have six minutes to identify as many lies as possible, using the text as their proof.