Fans of the films produced by Marvel Studios know: you have to stay through the end credits to catch the bonus scene. Sometimes, it’s just a humorous coda — like the Avengers getting bloated on shwarma after saving New York from angry aliens. Sometimes, it’s a teaser for the next film in the franchise (as was the case recently with Ant Man and the Wasp).

That’s savvy marketing: you’ve got the audience right there, so why not take a few moments to make them want to come back for the sequel?

But I don’t think Stan Lee invented the idea. In fact, one might argue that it goes back at least to the apostle John.

Read John 20:30-31 and 21:25. Both sound like endings; cue the orchestra, roll credits! Accordingly, some scholars believe that John’s original draft of the story ended with chapter 20, and that some or all of chapter 21 was added later. The debate, of course, is why. Chapter 21 gives us a vivid and memorable story, but what purpose does it serve? It’s a puzzle that doesn’t have a single solution that can be proven correct.

But I like to think of chapter 21 as a bonus scene that sets up the next tale to be told.

John’s story, after all, has always been about witness: who would testify to the truth about Jesus, about his origin and identity? Right off the bat, John himself boldly declared him to be the eternal Word made flesh (1:1-14). John the Baptist called him the Lamb of God (1:29, 36) and the Son of God (1:34; in some manuscripts, “the Chosen One”). And Jesus’ own miraculous works and compelling words should have been eloquence enough.

But many still did not believe — would not believe. His opponents would not listen to the testimony of John the Baptist, nor Jesus’ own testimony, nor the testimony of his works, nor even the testimony of Father (5:31-38).

As the time for his arrest and crucifixion drew near, Jesus told his followers that he would send them the Holy Spirit: the Spirit would continue to testify to the truth about Jesus, and would help the disciples to do the same (15:26-27). That would be their job: to continue to bear witness after he returned to the Father. And, of course, they would suffer for it (15:18-21; 16:1-4).

By the very end of the story — after the arrest, the trial, and the crucifixion, after the resurrection and the disciples’ almost comic lack of comprehension — it’s still about belief: “But these things are written so that you will believe that Jesus is the Christ, God’s Son, and that believing, you will have life in his name” (20:31).

And it’s still about the people who were called to continue to testify to the truth, empowered by the Spirit of Truth (15:26). Indeed, one of the emphases of chapter 21 seems to be the beloved disciple’s commission to testify to Jesus by writing the gospel itself (21:24).

The story, in other words, isn’t really over. A blockbuster sequel is already in the works. Want to know more?

Stay for the bonus scene.