Add the instant pudding mix to a medium mixing bowl. Pour in the cold milk and whisk for 1–2 minutes, until the mixture thickens slightly. It should be thicker than heavy cream but still pourable, similar to soft yogurt.

Slowly whisk in the cold alcohol (vodka, rum, or a combination such as Irish cream plus vodka). Scrape the sides and bottom of the bowl to make sure everything is well combined. The mixture may look a bit thin at this stage; it will continue to set.

Add the thawed whipped topping to the bowl. Using a spatula, gently fold it into the pudding mixture, turning the bowl and scooping from the bottom up. Avoid stirring vigorously so you keep the mixture light and airy. Fold just until the color and texture are uniform with no streaks.

Taste a small spoonful of the mixture. For a sweeter, lighter flavor, fold in an extra spoonful or two of whipped topping. For a deeper flavor, add a small splash of a complementary liqueur (such as Kahlúa for chocolate or amaretto for vanilla). Keep in mind that adding extra liquid can soften the final set, so add any liqueur sparingly.

Arrange the mini plastic shot cups on a small tray or baking sheet to make them easy to move. Use a small cookie scoop, piping bag, or a zip-top bag with a corner snipped off to fill each cup about 3/4 full, leaving room on top for garnish.

Transfer the tray of filled cups to the refrigerator. Chill for at least 2 hours, or up to 24 hours, until the pudding shots are set and spoonable but still creamy. For a slightly firmer texture, chill overnight.

Just before serving, garnish the pudding shots as desired: chocolate shavings or mini chips for chocolate shots, sprinkles or crushed vanilla wafers for vanilla shots, or a small dollop of whipped cream with caramel or chocolate drizzle for an extra fancy look. Serve on a tray or rimmed baking sheet so the cups don’t slide around.