Nifft
Penguin Herder
The Vorpal Tribble said:1 point of non-lethal if alive, 1 point of lethal if undead.
That's not what the spell says.
1/ Undead are immune to the spell because it's a Fort save which doesn't affect objects; and
2/ As written, only a successful Fortitude save causes "damage"... a failed save causes "non-lethal damage". They're different, you see.
Cheers, -- N