Lenny didn't ask for this heroic role! Amanda made him do it, she with her insistence on adopted progeny. Call it biological drive, but the paternal instinct, once awakened, couldn't prohibit the curiosity that comes with love.

Lenny: I’ll bet this kid has a dynamite mother. Chorus Leader: Curiosity that’s what kills us. Not muggers or that bullshit about the ozone layer. It’s our own hearts and minds. Lenny: I’m going to find out. Chorus: Please Lenny, don’t be a shmuck. Hear Lenny and the Chorus (168kb wav)

Aphrodite doesn't discriminate; she emboldens the unlikeliest candidates to heroic heights. But regardless of the mortal machinations, Fate succeeds in the end, and:

Love conquers all; let us too yield to Love.
(Omnia vincit Amor; et nos cedamus Amori.)

-- Virgil, Eclogues, X

It's a comedy, folks ;-) .