In Alien Nation the Tenctonese (or newcomers) can become intoxicated by drinking spoiled milk like humans do fermented fruit or alcohol. I didn’t actually have that in mind when I decided tryptophan works differently in Fizzbin’s people but there is a precedence for the joke.
Interestingly, turkey turns out to not have any more tryptophan than any other fowl, and that drowsiness at Thanksgiving may actually be blamed on the rest of the meal.