[Warning: This post spoils Guardians of the Galaxy Vol. 2. If you want to remain unaware of elements of that movie's plot, look away right now.]

The first mid-credits scene in Guardians of the Galaxy Vol. 2 is a classic "the gang gets back together for one last heist" scene, with Ravagers reunited in the wake of Yondu's death. But who are these characters, and why is it a big deal that they're joining up one more time?

To those who only know the Guardians through their movies, only two of the characters glimpsed onscreen were in any way familiar, and even that was purely because Stakar (Sylvester Stallone) and Martinex (Michael Rosenbaum, unrecognizable in his CGI-crystalline form) has appeared earlier in the movie to berate Michael Rooker's Yondu about his involvement in trafficking children — a scene which, until that point, had seemed little more than an excuse for a Stallone cameo and a way of laying groundwork for a later plot twist in the movie.

For comic book fans, however, Stakar's name — and Martinex's look — are clues that pay off in the mid-credits scene. Both are members of the first comic book version of the Guardians, as introduced in 1969's Marvel Super-Heroes No. 18 (Stakar wasn't part of the original lineup; he joined, under the name Starhawk, in 1975's Defenders No. 28).

Yondu, notably, was also part of that lineup — as were all of the other characters glimpsed in the credit scene: Michelle Yeoh plays Aleta Ogord — traditionally the adopted sister and also wife of Stakar, although whether Marvel Studios follows through on that comic book relationship remains to be seen — while Miley Cyrus voices Mainframe, an artificial intelligence evolved from the operating system of the Vision. The red dragon was Krugarr, a relatively obscure castmember from the same 1990s run that introduced the understandably maligned Taserface to the comics. Not present in that scene, but seen during the funeral scene, was Charlie-27, played by Ving Rhames.

Jim Valentino/Marvel Entertainment

That the movie versions of the characters are different from the source material is obvious. In comic book lore, these characters don't exist until a thousand years from now — each of the founding members represent planets colonized by humanity across the next millennium — and they're heroes, not thieves. (In general, the comic book versions of both Stakar and Yondu are far more straight-laced and traditionally superheroic than Gunn's takes.) But there's another difference between the two incarnations of this team that might be the most important — and, perhaps, offer a clue as to where the movie version is headed next: a missing character.

The original comic book Guardians was a four-person group. Audiences have met Martinex, Charlie-27 and Yondu, but the amazingly named Vance Astro remains absent. Astro is an important element of the larger Guardians franchise in comic format: not only was his arrival in the 30th century the inciting incident that caused the team to form in the first place, but his arrival back into the 21st century was one of the first storylines for the comic book version of Star-Lord's team, and provided that team with its name.

If James Gunn is using the original Guardians in some form in future projects, Astro not being around surely can't be an accident. Is there another former Ravager out there waiting for his big-screen debut? Or perhaps — just maybe — could Astro, or something related to him, be what the other Ravagers have gotten together to steal?

Guardians of the Galaxy Vol. 2 is in theaters now. For more, check out what that Adam tease means — and our interviews with Sean Gunn and Michael Rooker