Mark 3:13-18

Jesus went up on a mountainside and called to him those he wanted, and they came to him. He appointed twelve that they might be with him and that he might send them out to preach and to have authority to drive out demons. These are the twelve he appointed:

Simon (to whom he gave the name Peter)
James son of Zebedee
and his brother John (to them he gave the name Boanerges, which means “sons of thunder”)
Andrew
Philip
Bartholomew
Matthew
Thomas
James son of Alphaeus
Thaddaeus
Simon the Zealot
Judas Iscariot, who betrayed him.

Here we have a list of apostles.

Specificity

The sheer specificity makes me think the author saw this as a factual account, in that they thought the list of people sufficiently accurate to preserve, and knew them or knew of them. If the life of Jesus was a complete legend, there doesn't seem to be any particular reason to invent such a specific list. (Over 100s of years, yes -- look at the names of hierarchies of angels "deduced" from first principles. But probably not over 20-100 years.)

Judas

The gospel is structured as a record of historical writings: you get the feeling reading this, that the reader is expected to already know the story of Judas. If it were a novel it would be foreshadowing, but I don't think it is, it's just a pile of details all assembled into the most relevant/coherent order the author thought they could manage.

Peter, you are the rock

Here we have the bit where Simon aka St Peter is called "Peter". After a bit of googling, it looks like:

* Jesus and Peter probably talked in Aramaic
* Jesus dubbed Peter with a nickname meaning "Rock" in Aramaic, which was translated into "rock" in greek
* The greek used for "rock" sounded like "Peter", which was the presumed origin of the name Peter
* AFAIK neither the aramaic or the greek being a previous name (although I don't know if that's certain)
* Later on Jesus talks about "Peter, you are the rock on which I build my church"
* Which is sort of a pun, but not, because it seems "Peter" was a nickname anyway

So what actually happened? Was Peter nicknamed "Peter" for some unknown reason (eg. it was an affectionate nickname, it was a reference to rock for some other reason, etc)? Or did Jesus just say "you are the rock on which I build my church" and then everyone started calling him Peter? Or something else?

Aside

The details of Peter being the rock on which Jesus builds his church are disputed depending on which Christian tradition you follow, what exactly Jesus means by this analogy if he even said it, and it wasn't Peter putting words in Jesus' mouth. But I don't really follow the differences.