In many ways, Guardians of the Galaxy has been Marvel’s most surprisingly successful film. While most comic book properties are inherently fantastic and a more than a bit weird, Guardians moved things in a truly bizarre direction. The movie takes place almost entirely in outer space, and the main cast are constantly surrounded by wacky and wild alien races. In fact, four of the film’s protagonists are freaky aliens themselves, ranging from green-skinned humanoid to anthropomorphic trash panda.
That being said, there are dozens of fictional alien races to play with in the Marvel universe, and some are so weird that they definitely won’t appear in The Eternals, Guardians of the Galaxy Vol. 3, or any other corner of the MCU's cosmos. A few of the potential candidates are too visually bizarre to work on the silver screen, while others have traits that could only ever translate as straight-up goofy. The success of Guardians definitely broadened the potential types of stories that Marvel can get away with telling, but they’re not yet ready to explore the deepest and darkest corners of their fictional galaxy.
Doop has been floating around the X-Men titles for decades now, but fans have yet to fully understand him. Doop is ostensibly an alien, although his exact origins are a bit murky. He’s sort of like Marvel’s equivalent to Slimer from Ghostbusters.
Doop, however, has a much more defined personality that contains some unexpected quirks. He seems to have a never-ending array of fantastical powers, including the almighty power of seduction. Doop is often seen hooking up with both men and women, and apparently always leaves them satisfied, despite his blobbish appearance.
The Beyonder is a character with an extremely complicated history. He’s the guy who kidnapped a bunch of Marvel heroes and villains for the original Secret Wars. He then visited Earth for the sequel, Secret Wars II: 2 Secret 2 Wars, during which he adopted a human-like disguise that appeared to be based on Michael Jackson.
The near-omnipotent Beyond had the power to rewrite reality however he pleased, which made him too powerful to keep around for very long. He faded into the background, but it was recently revealed that he actually belonged to an ancient race of uber-powerful beings, creatively known as the Beyonders.
The character of Bi-Beast is super bizarre no matter how you look at him. Thankfully, he's not a weird comic book send up of bisexuals, but rather an android designed by an alien race. This makes his strange appearance even more inexplicable, because who would intelligently design a creature with two faces, with one on top of the other? Despite his goofy visage(s), Bi-Beast is actually insanely strong, and has gone toe-to-toe with both Thor and The Hulk.
The Mangog has had a... complicated comic book history. It’s pretty unclear as to whether or not he actually is an alien. Originally, Mangog was a being created from the stored-up hatred of the thousands of individuals that Odin, Thor’s father, had killed over the years.
Later on, he turned out to be a colleague of sorts to Thanos, the Mad Titan, and further stories even insinuated that Mangog was Thanos’s clone. Either way, he’s a freaky-looking and freaky-powerful monster that has given Thor a run for his money several times.