How did you break your arm?

“What the-when did you break your arm?!”
“Ooh, last sunday.”
“Dude, I was with you till 3 am and you didn’t had that!”
“Well, after I left from the party things got a little … weird.”
“I wouldn’t say that falling down the stairs while drunk would be considered ‘weird’”
“No no no! that wasn’t it, I swear it! You see, I was walking back home - mostly because I couldn’t call an uber, I didn’t have my phone and I still don’t know where it is-”
“Ooh, yeah, it fell from your pocket after we almost fell from the roof.”
“...I don’t remember that? what the fuck?! Why is it so sticky?!”
“...”
“Whatever, that doesn’t matter… now listen. So I was walking back home and I kinda got lost, just a little..”
“How little is ‘just a little’?”
“...I was around Tom’s place…”
“Dude! that’s like at the other side of town!”
“I was drunk and tired and alone, I had the right to get lost! Anyway, stop interrupting me. So I kept walking and then I saw this girl, she had this long dark hair, it looked so incre-”
“Dude”
“Yeah yeah, so she was there talking in her phone about… something, I don’t know, my brain wasn’t really working-”
“Your brain never works.”
“Shut up! So I got near her and asked where the hell I was, but I think my word got all slurred and she didn’t understand me because she stared at me like I was stupid, and she had this big black eyes, they were so pretty dude, it was like-”
“Stop, I want to know why you have a cast, not your failed romance attempt.”
“Hey! this time I didn’t failed because I didn’t even tried!”
“... I think that’s worse.”
“Shut up! Ok, so we stood there for like… 5 minutes and then a random car crashed into me!”
“You could have told me from the start that you were in a car accident!”
“No! it wasn’t that! The accident broke my leg, not my arm.”
“I think you are still drunk, we should be taking you back to the hospital.”
“See?! I told you it was weird! Because then this dude stepped out of the car and shouted at the driver and then shouted and the girl and I was also shouting because I had a broken leg and then I didn’t.”
“...what?”
“The dude from the car that had this super expensive suit told me he was sorry or something, I wasn’t paying attention because I was drunk and I had a broken leg and then I didn’t. So… I ran away and apparently I actually knew how to go back home because next thing I know is that I’m in the hospital with Dave telling me that I shouldn’t run up the stairs while drunk.”
“...Dude… Chris… ooh, god, just shut up. We have an exam next hour, I could do without your drunken dreams.”
“No no no no, I swear it was not a drea-what exam?”
“Chemistry? the teacher repeated like five times that the exam was today.”
“Oooh, god I’m so dead!”
…
“Mark, I swear I’ll break your arm when I come back. The kid from yesterday that Will crashed into? well, HE REMEMBERS IT. You should have wiped him out! I swear you are going to get us all into a psychiatric hospital at this rate… don’t shush me, this is your fault!... Ok, yes, Will was the one driving but you know perfectly well that he is a walking disaster, can you fire him already? … I meant a literal fireball!”