After all, here in America "The Archies" had a pop hit in "Sugar Sugar" despite being cartoon/comic book characters... so it's not like its without precedence. Fake bands abound... Milli Vanilli, The Monkeys... hell, I think even the Ninja Turtles did a rock concert tour.

Of course, even cartoon bands and such had always had actual performers behind them being brought into recording studios and singing the songs before this. Now you don't need to bother with that. While there was a voice actress somewhere who provided the base sounds for these programs, they likely have never uttered the phrases that make up the lyrics of any songs these artificial characters sing.

I looked up "Pink Lady" by the way, and Wikipedia seems to indicate that they were a living pop group in Japan that had animated adventures made about them or something. So they seem to be no more synthetic than your average pop star.