Background Voice: It's spa day,
A day to unwind,
We'll walk on your spine,
We'll be kind...

Background Voice/Ferb: It's—

(The song turns into a seaweed rap tune)

Ferb: Spa Day!
Phineas: Yeah!
Ferb: P & F on the scene!
Gonna slather you with mud and make you feel like a queen,
Got you sittin' in the hot tub—
Fireside Girls: Loungin'!
Ferb: You're thinkin' this place is a—
Fireside Girls: —stoundin'!
Ferb: Hot steam! Hot stones! Hot water! Hot wax!
We're pipin' cool new age music, can't help but relax!

(relaxing music plays)

It's a spa day,
Phineas: Yeah!
Ferb: Shiatsu—
Phineas: Gesundheit!
Ferb: Thank you very much,
We got a salt scrub, a mud tub; what's it gonna be?
A foot bath, a facial, aromatherapy!
Phineas and Ferb: (both inhale deeply) Yeah...
Aromatherapy!

Ferb: It's spa day!
Phineas: Yeah!
Ferb: Shiatsu!
Male Voice: Where ya from?
Masseur: I'm Pennsylvania-Dutch
Ferb: Sippin' cucumber water and a big slice of lime,
Throw your clock away, you're on P & F time! It's a—
Background Voice: Spa day!

http://phineasandferb.wikia.com/wiki/Spa_Day_%28song%29