Pro-Dueling - S2-E38
Other mistake: When Crowler and Bonaparte approach Damon and Mathmatica during their duel, Mathmatica appears to have 4000 life points. A couple minutes later, when Mathmatica loses 1000 life points due to Damon correctly guessing which card he would draw, Mathmatica's life points are now 3000 (which then go down to 2000). (00:04:33 - 00:06:53)