"One-Punch Man" and "Kekkai Sensen and Beyond" (Muscle Growth/Monster Transformation)

Thanks to Ian Ricky for finding and recommending this clip, which features "a muscle growth transformation from the villain Lord Boros":

Thanks to Shiron for recommending a pair of muscle growth scenes from Kekkai Sensen and Beyond episode 8. I've cued this video to start at the second one (at 16:12) since it's more detailed, but you can view the first scene at 11:53.





As a muscle growth bonus, here's a suggestion from lamarcodon, which he describes as "just a goofy little fun video I thought you guys might like":