It's Kind of a Funny Story

After contemplating suicide by jumping off the Brooklyn Bridge, 16-year-old Craig Gilner (Keir Gilchrist), decides to go to the hospital to seek help. Craig tells Dr. Mahmoud (Aasif Mandvi) that he needs immediate help to which Dr. Mahmoud registers Craig for a one week stay in the hospital's psychiatric floor.[2][3] At first, Craig is unsure if he made the right choice to stay, mostly due to the fact that his friends might find out when he misses school, especially Nia (Zoë Kravitz), his crush and the girlfriend to his best friend Aaron (Thomas Mann). Also, he is placed in the adult ward because there are too few teenage patients, and he understandbly feels uneasy and a bit scared being in the midst of so many adult psychotics.Craig is introduced to Bobby (Zach Galifianakis), an adult patient who claims he is only there on vacation, as he takes Craig under his wing. During a group discussion, Craig learns that Bobby is stressed about an upcoming interview in hopes of moving to a halfway house. When Bobby states that all he'll have to wear for the interview is the sweater he is currently wearing, Craig offers that Bobby could borrow one of his dad's dress shirts to wear, and Bobby accepts. Craig's kind offer to Bobby is witnessed by Noelle (Emma Roberts), another teenage patient who is in for self-mutilation. She is impressed by Craig and leaves him a note to meet with her that night. Later, Craig and Noelle attend a painting session for the patients. Craig paints a picture of an imaginary city map which he describes as like his own brain.Throughout his stay, Craig comes to a close bond with various patients on the floor including Bobby and Noelle. Bobby reveals to Craig that he is a father of a little girl and that he is actually in the ward for attempting to commit suicide six times. As Craig tries to help Bobby with his problems, Bobby, in return, helps Craig to gain the courage to ask out Noelle.One night, Nia stops by to visit Craig at the hospital, revealing that she and Aaron had broken up. Craig takes Nia back to his room where she tries to seduce him. However, the two are caught by Craig's roommate Muqtada (Bernard White), an old Egyptian man who has not left the room during his stay. As Nia runs out of the room, Criag chases her and calls out that he loves her, unaware that Noelle is standing behind him. Upset, Noelle storms off leaving behind a drawing of a self portrait that she planned on giving to Craig.Craig eventually wins Noelle's forgiveness, and the pair sneak out of the ward in scrubs and run around the hospital, ending up on the roof. There, Craig finally works up the courage to ask her on a date, and they kiss. On Craig's last night, he hosts a pizza party for the patients and helps Muqtada leave his room by playing Egyptian music for him to dance to. Craig also meets with Bobby, who got accepted into the home, and gives him a map of how Craig imagines Bobby's brain to be. Craig leaves the hospital the next morning not entirely cured, but with better aspirations to enjoy his life. He finally gains the courage to speak the truth to his father - which seems to be one of his main problems - perhaps the biggest problem. Dad wants Craig to be a big businessman, but Craig is more clearly cut out for the creative artistic life - painting and singing.

Question: What is the relationship between Craig and Aaron?
Answer: Best friends