Another major Hollywood star could be about to join the MCU. Considering the sources we'd take with a pinch of salt, but according to a Reddit user with 4Chan sources, The Greatest Showman star Zac Efron is being lined up for a major role in the upcoming Guardians of the Galaxy Vol. 3. The user revealed that he is being eyed to play the pivotal Marvel Comics character, Adam Warlock.
"Adam" was teased in the post-credits scene for Guardians of the Galaxy Vol. 2 when Ayesha of the Sovereign (Elizabeth Debicki) created a perfect being to take her revenge on the Guardians. So will Adam be a threat to the Guardians? In the comics, Adam Warlock (originally Him or Adam) was created by Stan Lee and Jack Kirby and debuted in a Fantastic Four issue in 1967.
Created by scientists called the Enclave, Adam was created as an artificial, perfect human, who initially calls himself "Him". After rebelling against his creators, and having a conflict with Thor, Him decides to leave Earth and travels into space. We know Thor is part of Guardians of the Galaxy Vol. 3 after he joined the team in Avengers: Endgame so they could interact.
Other leaks also suggested that the villain of the film would be the High Evolutionary, who helps to empower and transform Adam further in space. It is unlikely that the films will depict the comics characters' important relationship with Thanos in the comics as they are friends and also grave enemies.
Adam was the one to defeat Thanos in the original Infinity Stones story. Again, we'd take these with a pinch of salt but we have a wait to see if Zac Efron will be joining the MCU. Guardians of the Galaxy Vol. 3 does not currently have a release date.