Some Fallout TV show viewers think Amazon's series might have made two particular endings to Fallout 4 canonical in the wider universe.
Be warned: there are spoilers for Fallout 4's ending here and very light spoilers for the Fallout TV show!
In the opening episode of the Fallout TV show, the Brotherhood of Steel's massive airship dominates the skies above the faction's headquarters. Some viewers on Twitter are convinced that this airship is none other than the Prydwen, the Brotherhood of Steel's domineering airship from Fallout 4.
There are vying opinions over which bit of information actually confirms that this is the Prydwen. For one, the Fallout TV show Wiki names the airship the Prydwen, claiming the airship was still operating in the year 2296 during the Fallout TV show. The Wiki doesn't back up this claim with a confirmed source, however.
Others, meanwhile, claim that by zooming in on the stern of the airship, you can see the letters 'Prydwen' clearly inscribed on the huge ship. You must need a microscope to find these letters, though, because I've scanned the ship numerous times and I still can't clearly find them.
Our Fallout TV show Easter Eggs catalog has the Prydwen, which is originally from a Welsh poem called Preiddeu Annwfn, called the 'Caswennan' instead. Apparently this is merely another stand-in for the same name, however, so the airship being dubbed the Caswennan doesn't eliminate it from being the Prydwen.
Many Fallout game players are intrigued by what this possibility means for Bethesda's games, though. We already know that Bethesda considers the new Prime Video show to be canon in the wider Fallout universe, and if this is none other than the Prydwen, it potentially solidifies one particular Fallout 4 ending as canonical for the 2015 RPG.
The Prydwen is destroyed if the player voluntarily sides with the Railroad faction instead of the Brotherhood of Steel near the end of Fallout 4, and the Fallout TV show seemingly eliminates this possibility. However, it's possible to leave the Prydwen intact if the player sides with the Minutemen faction and eliminates The Institute, while avoiding making the Brotherhood and Railroad hostile factions.
If the airship in the Fallout TV show is the Prydwen, which many viewers seem to believe, it indicates the player character sided with either the Brotherhood of Steel or the Minutemen in Fallout 4. Bad luck if you were a big fan of the Railroad, though - it seems like the new TV show has pretty much overlooked the faction from Fallout 4.
Make sure to read over our Fallout TV show season 2 guide for a full look at everything that could happen in the next chapter.