Well, sometimes it's rather lyrical. In the .hack anime, the opening theme includes scenes of Aura in a bubble, like a womb, naked. Then later, as she unfolds, her dress starts billowing around her, like she was wearing it all the time. Very beautiful. And you never 'see' anything.
Also, an example in Digimon, outside the opening theme though, is when they biomerge in the third season. They absorb their d-powers into there bodies while naked, but they are drawn without anything perverse. It's just to show that they are completely giving themselves to their final forms, and allowing the fusion to complete.
That's how I saw it.