[ADAM]
Bum ba bum ba bum bum ba bum ba bum
Bum ba bum ba bum

[LADIES & DARREN]
Bah-da

[ADAM]
Bum ba bum ba bum bum ba bum ba bum
Bum ba bum ba bum

[LADIES & DARREN]
Bah-dow

[DB]
The bad trait
Will always predominate
Bad trait
Is certain to win
The bad trait
Will always predominate

[ALL]
That is the law of genetics

[DB]
According to Finn

[ADAM]
Bum ba bum ba bum bum ba bum ba bum

[ALL]
Bum ba bum ba bum bum ba bum ba bum

[ADAM]
Bum ba bum bum [LADIES]
Smart or dumb
Fat or thin
Lazy or not, lazy
We have
Lousy aesthetics [DB & DARREN]
The dumb will predominate
The fat will predominate
The lazy will predominate
We have
Lousy aesthetics [DB, SANDY, SALLY, & DARREN]
The bad trait
Will always predominate
Bad trait
Is certain to win
The bad trait
Will always predominate

[ALL]
That is the law of genetics according to Finn

Bum ba bum bum ba bum bum ba bum ba bum

[DB]
Why is the smart son always the gay son?

[SALLY & SANDY]
Finn's second law of

[SALLY & SANDY & DARREN]
Genetics [LADIES]
Smart or dumb
Fat or thin
Lazy or not, lazy
We have
Lousy aesthetics [DB & DARREN]
The dumb will predominate
The fat will predominate
The lazy will predominate
We have
Lousy aesthetics [ALL]
(staggered)
Bum ba bum bum ba bum bum ba bum ba bum
Bum ba bum bum ba bum bum ba ba dow!

[DB]
Say your father has a stomach
You are sure to get that stomach

[SANDY & SALLY]
It's a simple fact science

[ADAM & DARREN]
Don't rely on self-reliance

[ALL]
You are sure to get that stomach
So eat, eat, eat
Because the bad trait
Will always predominate
Bad trait
Is certain to win
The bad trait

[ADAM]
Will always predominate

[ALL]
That is the law of genetics
That is the law of genetics according to-
That is the law of genetics according to-

[ADAM]
B-B-B-B-Billy, B-B-B-B-Billy

[ADAM, DARREN, & DB]
B-B-B-B-Billy, B-B-B-B-Billy

[ALL]
B-B-B-B-Billy
B-B-B-B-Billy
B-B-B-B-Billy Finn!
Oh, Billy's law of genetics!