Okay… hear me out…
The little guy running naked while Jesus is being arrested from the Gospel of Mark + the Beloved Disciple from the Gospel of John = Same guy.
Disclaimer: I don’t know anything about anything, I’m just a guy who sees some gay shit* in the Bible and unlike a lot of Christians, I am Intrigued instead of Appalled.
*Yes, there will be gay shit in this post eventually.
So both of these figures, interestingly, are generally seen as the respective authors humbly not identifying himself. But literally the only reason people think that is because both of these characters are unnamed. It's a huge speculation. The "titles" of the gospels (which I will be using here) were later additions based on early Christians' guesses of who the author was/who the unnamed guy was, but neither guess can be backed up in the texts themselves.
Mark’s Streaker appears in two whole verses following Jesus’ arrest in the garden: “A certain young man was following him, wearing nothing but a linen cloth. They caught hold of him, but he left the linen cloth and ran off naked.” Mark 14:51-52