Okay, sorry, we'll start over. We just love us a Boston accent.
Chuckie Sullivan is Will's best friend… which is saying a lot because Will doesn't trust that many people. Chuckie's also a pretty witty guy in his own right, as we find out when he jokes with his buddy about a sandwich:
CHUCKIE: All right, well, give me your f***ing sixteen cents that you got on you now, and we'll put your f***in' sandwich on layaway.
On top of his wittiness, Chuckie is also one of the most loyal dudes you'll ever meet. The second he sees Will get ready for a fight, he follows him to help out and tells his other buddy, "Let me tell you somethin'. If you're not out there in two f***in' seconds, when I'm done with them, you're next."
When it comes to living in the streets, Chuckie knows what it means to have someone's back.
Despite his charm and loyalty, it's clear that Chuckie is not on the same intellectual level as Will. Will tries to close this gap by hiding his intelligence most of the time, but we can still see the difference when Chuckie says things like,
CHUCKIE: This is a Harvard bar, huh? I thought there'd be equations and s*** on the walls... I will take a pitcher of the finest lager in the house.
He also needs Will to save him when a jerk from Harvard named Clark starts making fun of his intelligence. Usually, Chuckie would just pull the guy outside and fight him. But at Harvard, he's not he's not on his own turf and he can't settle things the way he's used to.
For the most part, it seems like Chuckie's happy to have Will around all the time. But it's only at the end of the movie when he reveals what he really thinks of Will's approach to life. He tells Will that he's wasting his potential working construction. But when Will asks if he owes it to himself, Chuckie answers,
CHUCKIE: You don't owe it to yourself. You owe it to me. 'Cause tomorrow I'm gonna wake up and I'll be fifty. And I'll still be doin' this s***.
In Chuckie's mind, Will's life is an insult to all the men who work construction and wish they could be doing something else. Chuckie makes this clear when he says that the best part of his day is going to pick Will up in the morning and hoping he won't be there.
At the end of the day, Chuckie is a good enough friend to know that Will needs to escape their childhood neighborhood and go out to do great things. He also gets his wish in the movie's final scene, when he walks up to Will's door and realizes that Will has taken off. Chuckie doesn't know where Will has gone and he doesn't need to know. He's just happy that Will has finally decided to get out of their neighborhood and see the world beyond it.