He gained the nickname "Mouch" because he is almost always, other than when he is on calls, seen watching television on the couch. The nickname is a mashup of Man and Couch, and the other firefighters call him "half-man, half-couch".
Mouch is the current Firefighter's Union President - he is responsible for raising issues that firefighters face to the Fire Department, the City of Chicago and the State of Illinois.
He is also a union representative and goes with members of Firehouse 51 as their representative at disciplinary hearings.
In Season 5, Mouch tried to help Cruz with a legal problem. However, he soon discovered that most of his old contacts had retired and that his old tricks no longer worked. Cruz lashed out at him for not being able to help and told him he was old and not good at his job, as Mouch had assured Cruz he wouldn't get in trouble, which he did.
In the finale of Season 5, Mouch decided he would retire and that the call was his left. Herrmann wasn't happy to hear this. Inside the warehouse fire, everyone inside got trapped in after the fire escalated. Mouch suffered a heart attack and stopped breathing. Herrmann continued CPR on him the whole time they were inside, despite being burned.
Mouch returned to Firehouse 51 after deciding he would not quit. No one knew that he was about to leave until he told them. Cruz felt guilty about saying those things to Mouch and so he tried his best to give him everything he needed, and Herrmann told Mouch to stop taking advantage of him.
Mouch decided he would eat healthy and even entered 51 into a sports competition. When they complained, he finally told them that this was his family and that when he thought he was going to die, he regretted not spending more time with them.
For Joe's birthday, Mouch called his brother, Leon, back from hiding after confirming it was safe with Trudy. Otis and Herrmann knew about the plan but were uneasy about following it, because some people had seen Leon. Cruz went into a state of panic when he heard this, and this only escalated when he couldn't get hold of Leon. Cruz even asked Otis to come with him to check out the prime spots with him to see if Leon was back. However, at his birthday party at Molly's it was revealed that Cruz had figured out that Leon was back and was using his fake panic to trick Mouch.