Slimer! And the Real Ghostbusters Intro
Found by YouTube user DirRudy, here's a high quality version of the second version of the intro for seasons 6-7.
Slimer: (screaming) If there's something strange In your neighborhood, Who you gonna call? Ghostbusters! If there's something weird, And it don't look good, Slimer: Uh-oh! Who you gonna call? Ghostbusters! Slimer: Luigi, jump! Whoa! I ain't 'fraid of no ghost! Slimer: (screams) I ain't 'fraid of no ghost! Slimer: Ghostbusters! Yeah! Who you gonna call? Ghostbusters! Slimer: And me! And me!