The Marvel Cinematic Universe is a well-oiled machine at this point, consistently treating fans to new content in theaters and streaming with a Disney+ subscription. Anticipation for the next upcoming Marvel movie Avengers: Doomsday is sky high, and there are countless theories and rumors about what The Russo Brothers have up their sleeves. Fans are especially curious about what characters might appear, and some think they've found evidence of Ryan Reynolds' Deadpool being included. Let's break it all down.What we know about Avengers: Doomsday is super limited, which is why moviegoers are filling in the blanks with theories and rumors. The Doomsday cast announcement confirmed a ton of characters, but fans are still hoping for some surprise appearances. They have been wondering if Deadpool will appear in either of the next two Avengers flicks, and some fans think they got a hint at his role thanks to new merchandise.There's plenty of tie-in merch coming out ahead of Doomsday, and that includes a collaboration with designer sunglasses Ray-Ban. The brand just released a variety of Marvel designs, including a pair of Deadpool sunglasses. Some people online are seeing this as a hopeful update that Wade Wilson might get in on the crossover fun of the forthcoming blockbusters. (Image credit: Marvel Studios)This is just a theory at this point, so we should probably take it with a grain of salt. Still, there's been chatter about Deadpool being in Doomsday for months now, with Ryan Reynolds personally adding fuel to the fire. The character is wildly popular, so why wouldn't the studio want to bring the Merc with the Mouth into an Avengers movie or two?Wade Wilson finally joined the MCU with Deadpool & Wolverine, which broke box office records when it hit theaters. Given the movie's success, folks assumed that both Ryan Reynolds and Hugh Jackman would be continuing to play their signature characters for the foreseeable future. It would be thrilling to see them pop up in an Avengers movie, but only time will tell if that actually happens.To be fair, it's possible the Ray-Ban Deadpool glasses are a response to the character's popularity, rather than being directly connected with Doomsday. Although Kevin Feige teased that more characters would be in the movie, so this chatter will likely continue until its release this December. Fans are also wondering about whether or not Spider-Man will pop up as well, especially after Brand New Day's credits scene.All will be revealed when Avengers: Doomsday hits theaters on December 18th as part of the 2026 movie release list. I'd love to see Deadpool included now that he's in the shared universe, so I'll keep my fingers crossed that he gets that long-awaited crossover moment.