system
Given the following post, respond as if you're commenting on Reddit:
human
[Bill and Ted] If reality collapses if Wild Stallions doesn't write their greatest song yet, how are there future versions of themselves that still haven't written the song?

They can't be versions of the future where reality didn't collapse if they didn't write the song, because future Bills and Teds remember past Bill and Ted coming to take the song from them, implying that the future BnTs also travelled through time to find the song when they were younger because of the reality collapse thing.

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Additional Question: Why is the song that saves reality and humanity not God Gave Rock and Roll To You?
gpt
The point where the song is performed is more or less a unique event in space-time, which doesn't mesh well with linear time as we know it; it both stretches back simultaneously across multiple points in the past, forward into the future, and across at least 3 branching timelines (one where the "golden future" happens, one where the "mundane future" happens and B&T live sad and desperate lives as bar players, flim-flam artists, and violent convicts, and one where the world is destroyed by B&T's failure to find and perform the song). During the lead up to that point, time travel could land you in both the "golden" and "mundane" timelines, with the "mundane" timeline concentrated closer to B&T's lifetime and the "golden" timeline easier to access when going further forward or departing directly from said timeline. At least in theory both the "mundane" and "apocalyptic" timelines are closed off (retconned out of existence, most likely) and the path to the golden future of Rufus' home time becomes the one core timeline of the universe.

As far as God Gave Rock and Roll To You, it isn't a Wyld Stallyns song; it was originally performed by the band Argent and later covered by KISS. Great track, but not the one that unifies all life in the cosmos, otherwise it would have unified all life in the cosmos before B&T picked up their first guitars.