Venom: Let There Be Carnage revealed just how easy it could be to add Ryan Reynolds' Deadpool to the MCU. The Marvel Cinematic Universe is expected to reboot most of the Marvel characters acquired in the purchase of 20th Century Fox, particularly the X-Men, but with Ryan Reynolds expected to reprise Deadpool, it's raised a number of questions regarding how the MCU will handle Deadpool canon.
While many of Fox's Marvel movies were hit and miss, both of Deadpool's movies were well received. While it may be complicated for the MCU to bring all the existing X-Men actors to the MCU, Ryan Reynolds' portrayal of the Merc With a Mouth was too popular to resist, leading to big questions about how this will affect his franchise, since it takes place in one of Fox's X-Men (even though Deadpool's canon might be even more complicated).
There have been a number of teases about connections between Sony's non-Spider-Man Marvel characters and the MCU, including Michael Keaton's Adrian Toomes showing up in the trailer for Morbius, but audiences were still surprised by the post-credits scene of Venom: Let There Be Carnage, in which Eddie Brock and Venom are suddenly transported to the MCU. Doctor Strange in the Multiverse of Madness and Spider-Man: No Way Home will both lean heavily into the multiverse, creating opportunities for Marvel characters to hop between franchises, but Venom: Let There Be Carnage shows they don't necessarily need a complicated explanation (at least night right away) when there can simply be a flash of light followed by the character finding themselves in a new reality.
It may seem incredibly basic, and there will surely be more explanation coming down the road, the mechanics at play may be less interesting to many audience members than simply having these characters share the same universe, especially with someone like Deadpool, who'll surely have his own commentary about the hop between universes. It's doubtful Venom's multiversal hop will remain unexplained forever, but audiences embracing the shift without seeing anything more than him licking Tom Holland on a TV screen suggests it's not a huge priority.
This simple multiverse hop doesn't have to be reserved for just Venom and Deadpool, either. If Marvel Studios wants to use any popular Marvel characters from outside the MCU, now that Venom has paved the way, they can simply hop them in and out as needed, with Doctor Strange likely handwaving the reasoning away later in a separate movie. Whether this approach is good or bad for the MCU all depends on what they do with the characters once they make the jump, but thanks to Venom, we now know it's a lot easier than it looks.