It seems like the filmmakers decided to just throw caution to the wind in “Quantumania” and go full-tilt M.O.D.O.K. without really nailing how to adapt his inherently ridiculous design (the way “Captain America: The Winter Soldier” did with Arnim Zola’s digitized head). He’s got two basic modes in this movie: one where he looks tolerable but sounds iffy, and one where he looks unsettingly strange but sounds tolerable.
Some comic book illustrations of M.O.D.O.K., like Eric Powell’s cover art for “Super-Villain Team-Up: MODOK’s 11” #1, have depicted him as sinister and red-eyed, almost prune-faced like Thanos. MODOK does look sinister in his armored “Quantumania” form, but they do a metallic effect with his voice, and it just doesn’t work.
The character of M.O.D.O.K., created by Jack Kirby and Stan Lee, made his first full appearance in “Tales of the Suspense” #94, where his face was likewise wrinkly and sucked in on itself below an oversized forehead with a mutated brain inside. That’s the thing about M.O.D.O.K.: he’s super smart, not just someone whose defining trait is “being a dick.” Historically, M.O.D.O.K. served not as Kang’s disposable henchman, but as the leader of A.I.M. (Advanced Idea Mechanics). But “Iron Man 3” already showed Guy Pearce’s Aldrich Killian leading A.I.M.
Bringing “Darren” from the first “Ant-Man” movie back in “Quantumania” does bring this unlikely superhero trilogy full circle, but it also means M.O.D.O.K. and the unpopular Yellowjacket are the same villain, who’s now reformed and dead. That has the effect of shrinking, Ant Man-style, what is already a tenuous rogues gallery in the MCU.
About the only thing that feels right about Yellowjacket/M.O.D.O.K. in “Quantumania” is his line, “At least I died an Avenger.” In the comics, the Hank Pym version of Yellowjacket actually was an Avenger.