These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Covered Up - Everyone seems to remember that "Everytime We Touch" is a cover, but not many know the original. It was by Maggie Reilly. And "Faded" was originally an even more obscure song by Australian singer Kate De Araugo.
"What Hurts The Most" is an aversion. Rascal Flatts' version was the biggest hit in the US, but Cascada's was the bigger hit everywhere else.
Face of the Band - Natalie Horler, to the point where people think her name is Cascada.
Misattributed Song - Mainly songs remixed by the same DJs to sound like Cascada but aren't actually done by them.