In one episode of Fool Us, when Penn and Teller are performing a trick of their own at the end, Penn establishes that Teller (who is supposedly doing a card trick) has not really lost the card picked by a woman in the audience in the deck. Then he cuts the deck himself and asks her again if she is now satisfied the card is lost. When she responds yes, he shouts, "Wrong! No matter how nice I am to you, or how mean I pretend to be to this man here, my first allegiance in the world is to my partner!" Despite that this was all part of the act and the rest of the routine is about Penn bullying Teller to the point that Teller stabs him through the hand with a knife, that one line is clearly actually true and really sums up the level of trust involved in such a close, lasting professional relationship.
Another episode of Fool Us has a fifteen-year-old boy, Daniel Kramer, performing. Though he doesn't fool them, Penn's speech after his performance is pure warm fuzzies.
In their China trip in Magic and Mystery Tour, Penn and Teller befriending a family of Chinese magicians, with an uncle of the family giving them an eye-poker tool as a gift. Teller would later show off his eye-poker in an interview footage.
Penn and Teller have sponsored a "13 Bloody Days of Christmas" blood drive in Las Vegas for many years, including free show tickets for all blood donors.
One aspect of Fool Us that might be overlooked is the fact that while Penn and Teller might not be fooled by a contestant's act, they are very careful not to reveal the secret of the trick to the audience.
One specific example is Reuben Moreland, who had a variation of a trick involving dice that Penn admitted he was not a fan of, but loved how Moreland gave it his own twist. Declaring that Moreland "should do this trick for the rest of your life. Take it to your grave," rather than say out loud how they knew the trick, Teller wrote it down, and after Moreland acknowledged that they were right, Teller destroyed the paper he had written on.
Quite a few of the acts that appear on Fool Us admit that they probably have no chance of fooling Penn & Teller, and are simply content to appear on the show and perform for the duo, who are often named as an inspiration for getting into the business. For their part, Penn & Teller are not at all shy about doling out the praise if they like the act, whether they're fooled or not.