Mushrooms are so toxic and usually fatal, because there are usually no signs of poisoning until the mushroom reaches the small intestine. As a result, unlike other poisons that can be treated by stomach pumping, the mushrooms are already absorbed into the person's system so that only symptoms can be treated.
Jordan Knight, longtime friend of Donnie Wahlberg's is an extra in this episode. He can been seen at the precinct behind Esposito during a scene with Wahlberg.