Lyrics:

(As performed during the show, with piano and percussion:)

Michael: Lisa, it's your birthday.
God bless you this day.
You gave me the gift of a little sister,
And I'm proud of you today.

Michael and Bart: Lisa, it's your birthday.
Happy birthday, Lisa.
Lisa, it's your birthday.
Happy birthday, Lisa.

Michael: I wish you love and good will.
I wish you peace and joy.
Bart: I wish you better than your heart desires.
Michael: And your first kiss from a boy.

Michael and Bart: Lisa, it's your birthday.
Happy birthday, Lisa.
Lisa, it's your birthday.
Happy birthday, Lisa.

Bart: Yeah!

As performed over the credits, with full musical back-up:
Michael and Bart: Lisa, it's your birthday.
Happy birthday, Lisa.
Lisa, it's your birthday.
Happy birthday, Lisa.

Michael: I wish you love and good will.
I wish you peace and joy.
Bart: I wish you better than your heart desires.
Michael: And your first kiss from a boy.

Michael and Bart: Lisa, it's your birthday.
Happy birthday, Lisa.
Lisa, it's your birthday.
Happy birthday, Lisa.

Bart: Take it away, Lis.
(Lisa does a saxophone solo)

Michael and Bart: Lisa, it's your birthday.

(Lisa plays some more)

Michael and Bart: Happy birthday, Lisa.

Michael: Hoo!