Pokemon unite be like:

You wouldn't know this since you don't play UNITE, but the outfits Pokémon wear in that game are actually holowear. They're not physical and are instead holographically projected onto the Pokémon. Game lore states that they didn't want Pokémon to be uncomfortable and encumbered but still wanted them to "have pizzazz", so Nucleon wouldn't even feel the dress on him. (Iirc, it's suggested that the Pokémon get to decide what they want to wear more so than the trainer, so I like to imagine Nucleon there wanted to wear it haha.)