Found the lyrics to the intro-
Hey paisanos! It's the Super Mario Brothers Super Show!
We're the Mario Brothers, and plumbing's our game
We're not like the others who get all the fame
If your sink is in trouble, you can call us on the double
We're faster than the others, you'll be hooked on the Brothers Unh!
H-hooked on the Brothers. Gimme gimme, gimme gimme.
Yo, you're in for a treat, so hang on to your seat
Get ready for adventure and remarkable feats
You'll meet Koopas, the Troopas, the Princess, and the others
Hangin' with the plumbers, you'll be hooked on the brothers to the brink!
I say a h-h-h-h-hooked on the brothers! [echo and fade out http://www.retrojunk.com/details_theme/1/
You can also download the intro from that link