The Avengers: Doomsday trailer ends with a scene of Steve Rogers reuniting with Thor for the first time in years. The last time the two characters shared screen together was in Avengers: Endgame. If you remember, that movie also ended with Steve Rogers deciding to go back in time and live a life with Peggy Carter.Thus, when we see Steve in the present in Endgame, he has grown old and passed on the Vibranium shield and "Captain America" title to Sam Wilson. But, now, young Steve Rogers is back in Avengers: Doomsday, and this return has fans confused.Many believe that the Steve Rogers seen in the trailer is the same Cap we saw in Endgame, but he has traveled back in time. However, that's not the only popular theory.The Steve Rogers seen in the Avengers: Doomsday trailer might be an evil variant: View this post on Instagram Instagram PostSome believe that the bearded Steve Rogers we saw on this trailer is "HYDRA Cap," the evil Captain America variant who was a part of HYDRA. This controversial version of the character debuted back in 2016 with the Secret Empire event comics, and he hasn't appeared in the comics that much. But the controversy around the storyline kept this specific version of the character in conversation.Therefore, some think that the bearded Steve Rogers might be HYDRA Cap or an evil variant who probably would go onto attack Thor after managing to summon the Mjölnir in the final version of the scene of Avengers: Doomsday.Many point to the use of the multiverse and Robert Downey Jr.'s Victor Von Doom (not Tony Stark) as a reason that other characters, like Steve Rogers, could also have evil variants. The different appearance of a bearded Steve Rogers could hint that he might be an evil variant.Steve in the first teaser | Image Via: YouTube/Marvel EntertainmentThe very first Avengers: Doomsday teaser from December showed us a clean-shaven Steve Rogers, who looks like he did Endgame. We also see Loki inside a home; many believe it to be Steve Rogers'. Fan theories suggest that Steve's decision to stay back in time could've caused an incursion, prompting Doom to hunt him down. Thus, Loki would convince Steve to re-locate to a different reality for his and his family's safety.What else do we know about Doomsday? View this post on Instagram Instagram PostMuch like Avengers: Infinity War and Endgame, Doomsday would lead to next year's Avengers: Secret Wars. We know that Doomsday will follow heroes from three different universes trying to stop their respective Earths colliding with each other, which would destroy them all. These three Earths are:Earth-10005: The 2000s X-Men film franchise continuityEarth-828: The Fantastic Four: First StepsEarth-616: The MCU EarthThe official synopsis confirms that these three Earths are on a destructive collision course and the looming threat of Victor Von Doom. It reads:"'Avengers: Doomsday' follows beloved heroes from three distinct universes as they’re set on a deadly collision course and face an existential threat unlike anything they’ve ever encountered."What are your theories about Steve Rogers' role in Doomsday, and are you excited for December?