Okay, this is an awesome Wario Land reference...

[cheat-master30]

Old, but the music from Paper Plane is from the Curious Factory in Wario Land 4:

See 1 minute 9:

www.youtube.com/watch?v=Us-rUEd_0A8&feature=related

Wario even says quotes from the game as you see him in the windows.

Not the first music reference either:

www.youtube.com/watch?v=O3q4Ku01JRw

See the music about 50 seconds in. Sure sounds familiar:

www.youtube.com/watch?v=dUozK4yYwOY

Unfortunately, if there are more references, they're a pain to find, because Mario Wiki never lists references to the Wario Land games from future games (or to past games).

[cheat-master30]

Haven't logged in there for ages and don't want to reset my password yet.

That, and it could make good material for an article somewhere.