At the end of 2020's EQUAL AND UNEQUAL VECTORS OF AUTHORIAL WILL PT. 2, I wrote:
The same dynamic also applies to those serials that often or always focus upon “guest stars”who never again appear in the series. Early installments of Will Eisner’s SPIRIT are structured like almost every other adventure-hero feature, in which the Spirit helps good people and vanquishes bad people. However, even in the earliest years Eisner sometimes devoted stories to one-shot characters who seemed to take center stage, in that their triumphs or tragedies received the most attention. However, the Spirit was still the thread holding all of those one-shot characters together, and so he retained the greatest stature, even in stories like THE CURSE, in which the hero barely appears. As discussed in HOSTS, HEAVENLY AND OTHERWISE, the only exception to this centricity formulation appears in certain anthology titles. When a continuing character merely appears as an interlocutor—Jorkens in Arthur C. Clarke’s TALES OF THE WHITE HART, or the many “horror hosts” in comic-book titles—then whatever focal presence inspires the most conviction in each story possesses the greatest stature-vector, though not necessarily the greater charisma-vector.
But, it's occurred to me from time to time, what if the interlocutor telling the stories is also a part of them, as the Spirit always has potential agency in the anthology-stories in his series?
My conception of "agency" came up at the end of last year, with GOLDEN AGENCY PT. 1, where I defined the term thusly:
..."agency" will be used to describe interordination comparisons, which will be seen to possess both narrative and significant values.
The relevance of such comparison to the current question goes like this: if the Spirit can have dominant agency even in all of his stories, even those where he does next to nothing, then why would the same NOT be true of icons who appear in all the stories within a self-contained anthology?
In the above essay, the reason I split agency into both "narrative" and "significant" values was because it's more than evident that central characters may have no agency at all within the diegesis of their stories, but may have it in an extra-diegetic sense. My example was Willy Loman of Miller's play DEATH OF A SALESMAN, who has no power within his story to change his circumstances, but has agency insofar as his fate manifests the primary concerns of the author's will. Similarly, though the serial character of The Spirit may not have much narrative agency in all of his stories, he has significant agency as the source of the authorial ethos that ties together all the characters in his world.
So, when an interlocutor-like character participates within the diegesis of a story, one must ask if the author's will is most fully expressed in this icon's actions and outcome.
The 1981 HEAVY METAL presents viewers with a frame-story in which a glowing green sphere, billed in credits as "Loc-Nar," accosts a young girl, whose father he has just killed, and tells her stories about the many ways Loc-Nar has spread, or tried to spread, evil throughout the universe.
In one of the narrated stories-- which the listening girl views, as if Loc-Nar were a crystal ball-- Loc-Nar has only a minor effect, encouraging a robot to go sex-mad in "So Beautiful, So Dangerous."
In two stories, "B-17" and "Captain Sternn," Loc-Nar wreaks capricious changes on human beings, reviving dead pilots as zombies in "B-17" and mutating a not-quite-innocent individual in "Sternn."
In the story "Harry Canyon" Loc -Nar, pretending to be a priceless artifact, leads two subordinate characters to their doom. However, the centric character is never even aware of Loc-Nar's power, and fortune so favors him that he makes a pile of money off the weaknesses of those who seek to profit from the artifact.
In the other two stories, "Den" and "Taarna," Loc-Nar's influence takes different shapes. The entity does not directly seek to tempt the heroic Den, but other characters present Den with the possibility of using Loc-Nar to rule his new world, and Den nobly refuses.
In "Taarna" Loc-Nar seeks to dominate an entire future-world. Some denizens of that world summon the heroine Taarna to oppose Loc-Nar's forces, and after several battles, Taarna makes a direct assault upon Loc-Nar. The entity makes its only direct attempt at temptation, offering Taarna rulership, but the warrior-woman destroys Loc-Nar-- which, through some unfathomable resonance, causes the interlocutor Loc-Nar in the frame-story to perish as well. The movie ends upon a triumphant note, even though of the six stories, Loc-Nar succeeding in promulgating evil in three narratives, but did not wholly succeed in the other three.
In essence, the same paradigm applies to Loc-Nar that applied to Willy Loman. Loc-Nar has considerable narrative agency, but the point of the author(s) is to show that his agency can be defeated, and so in each story the centric icon is whatever entity the Loc-Nar impinges upon. Therefore he does not have significant agency across all six stories, as the Spirit does in all of his tales.
However, some of the characters appeared in other comics-stories before their adaptation in HEAVY METAL, and of course Loc-Nar, as conceived by the movie's authors, did not appear in the stories of "Den," "Captain Sternn," and "So Beautiful So Dangerous." Therefore, since these are "familiarity icons" being "crossed over" with the "novelty-icon" of Loc-Nar, HEAVY METAL qualifies as a crossover-film.
(Note: the name Loc-Nar comes from one of the "Den" comics-stories but there's no connection between that name and the movie's icon. Additionally, though Wiki says that "Harry Canyon" and "Taarna" are derived from two separate Moebius stories, neither qualifies as an adaptation.)