An American mathematician by the name of Tom Lehrer has been said to have been the 1st to create the jello shot in the early 1950s while working for the NSA, where he developed vodka jello as a way to circumvent a restriction of alcoholic beverages on base, but this claim has not been confirmed as yet.
The maximum alcohol content is somewhere between 19 and 20 oz. of vodka per 3 oz. package of Jell-O powder, or about 30% (ABV) alcohol by volume.
Alternatives
A few gelatinous desserts can be manufactured using agar instead of jello, allowing them to set far quicker and at higher temperatures. Agar, a vegetable product made from seaweed and is used especially in jello powder mix for a quicker setting time and Asian jello desserts, but also as an alternative that is acceptable to vegans and vegetarians. Agar is more closely related to pectin and other gelling plant carbohydrates than to ordinary gelatin.
There is one other vegetarian alternative to gelatin which is carrageenan. This alternative sets harder than agar and is often used in kosher style cooking. Though it, too, is a type of seaweed, it does not to have a bad smell when being cooked as agar sometimes has.
Chemistry
Fresh pineapple contains the enzyme bromelain which must can never be allowed to mix with the jello shot mix as this enzyme will prevent the jello from setting, this is common in most citrus and tropical fruits. Papaya and pawpaw contain the enzyme papain, kiwi fruit contains actinidin, and figs contain ficin- all with similar effects. Cooking denatures the enzyme, rendering it inoperative