Enter at your own peril,

Past the vaulted door,

where impossible things may happen, that world has never seen before.

(EDIT: Alright, since no one is guessing, here is the rest of the lyrics.)

IN DEXTER'S LABORATORY, LIVES THE SMARTEST BOY, YOU'VE EVER SEEN!

BUT DEDE BLOWS HIS EXPERIMENTS, TO SMITHEREENS!

THERE IS GLOOM AND DOOM WHILE THINGS GO BOOM!

IN DEXTER'S LAAAAAAAAB!