Matt Smith's Milo suffers from the same rare blood disease that torments Jared Leto's titular character. As a result of the experimental treatment Milo turns into a vampire. Unlike Morbius, Milo enjoys his new life, which results in his uncontrolled dancing in several film scenes.
According to Smith, all his dancing wasn't originally in the script and even wasn't choreographed. The 'Morbius' director, Daniel Espinosa, just let the actor "play around and discover things and take risks".
"It's rare on a film of that scale for someone to do that. So I was really grateful for that", Matt Smith says in his interview to GamesRadar+.
Some fans think that Smith's dancing was actually the best part of 'Morbius':
…but others find it embarrassing:
And here's a little something for the future: