Fourth Wall: If your character knows/reads Harry Potter, please do not tell Sirius that he is actually a fictional character. Also, please don't tell him anything beyond his canon point. Don't tell him that he's going to be arrested, about Peter, that he's going to die, etc etc. Thank you!
Threadjacking I LOVE IT! I am an awesome threadjacker.
Backtagging: I am also an awesome backtagger. I live off backtagging.
Mind reading: Yup! Go ahead
Telepathy: Also okay!
Special/magical items: DEPENDS. Let me know what they are, and I'll tell you.
Fighting capabilities: Sirius has a short temper and will definitely fight back. He's also a master at some embarrassing hexes and knows how to hold his own in a duel.
Injury/death: Injuries are okay, but it depends on the situation so please ask first. Death is a no, sorry!
Medical/physical info: Nothing that stands out. He's good looking, has gray eyes, and a wicked smile.
Relationships/Romance: Sirius is a little hard to get into a real relationship. He likes to flirt and mess around. So, it's possible, but don't get your hopes up!
Sexual Relationships: This is Sirius, so yes. Although I will not thread it out, sorry!
Physical contact Of course!
Right, that's pretty much it! Please just be wary of fourth wall! And if you have any questions, feel free to contact me!