Just like every other Marvel movie, 'Multiverse of Madness' has a couple of post-credits scenes that are definitely worth staying in your chair until the very end.
If you have yet to see 'Multiverse of Madness',
MAJOR SPOILERS AHEAD!
One of the following scenes is actually very important for the MCU future (and Steven Strange personally), and another is just fun.
Let's start with the 'Multiverse of Madness' mid-credit scene featuring a surprising cameo by Charlize Theron. It's important to note that during the movie Steven Strange uses dark magic several times, and by the end of the movie we see him struggling with the consequences of that choice. The movie itself ends with Steven Strange succumbing to the dark magic: a third eye opens on his forehead, just like one that Sinister Strange had. So the mid-credit scene begins with Doctor Strange still getting corrupted by the dark magic, and then Clea, Charlize Theron's character, appears. She asks Steven Strange for help, because someone very powerful threatens to destroy reality.
While being not all that long, this post-credit scene is pretty important, given how it introduces Clea into the MCU. In Marvel comics Clea is Steven Strange's love interest (with Christine Palmer seemingly being out of the picture now, maybe it's time for Steven to finally date someone new?) and the daughter of Umar, a major adversary to Earth's Sorcerer Supreme and Dormammu sister.
At this point it's not clear who Clea refers to, but many Marvel fans believe that it's Kang the Conquerer, the next Big Baddie in the MCU – or maybe Dormammu, who we've already seen in 'Doctor Strange' back in 2016. It actually seems like an even more solid possibility, given that Clea is related to Dormammu in Marvel comics.
There are two post-credit scenes in 'Multiverse of Madness', and the second one is all good fun, no heavy meaning or foreshadowing. It's just Bruce Campbell's character, who we've already seen in the movie, still selling pizza balls and joking about it. Looks like he's still in Illuminati alternate universe, but nothing of importance happens.