I had to google it. When a person not involved in the case filed a brief because they believe they have relevant information that might sway the appeal in a certain direction.
So Nick would file on behalf of Vic.
Right. Nick is attempting to act as an amicus curiae (literal translation: "friend of the court"), a non-involved (ha!) third party bringing up to the court what they believe is relevant information regarding the case.
Now that being said, there are rules for an amicus brief, like everything else in how a case works. Filing deadlines were months ago, in fact the final ruling is expected to be made sometime this week (although it will be finalized this week, the actual announcements won't be made until early next year). There's also some talk that in Texas, to file an amicus brief, you have to be authorized to practice law in the state of Texas, something Screech is definitely not able to do.