Line your baking sheet with wax or parchment paper and set aside. Pour about 1/4 cup of sprinkles into a small bowl or plate and set aside.
Combine chocolate and oil (if using) in small microwave safe bowl and heat on HIGH for 30 seconds. Stir and return to microwave for another 30 seconds. Stir to make sure all pieces are melted. If you still have a bit to go, continue in 15 second intervals until chocolate is fully melted.
Dip marshmallows halfway in chocolate and then gently tap the chocolate side of your marshmallow into the sprinkles until it is covered and place sprinkle side down on your wax paper lined baking sheet. Continue until you have the amount of marshmallows you want or you run out of chocolate (whichever comes first).
Put baking sheet in refrigerator (or freezer) until chocolate hardens.
Don't like sprinkles or just want to switch it up? Add some crushed pretzels or peanuts, coconut shreds, or almond slivers to them instead. Want to get even fancier? Drizzle some peanut butter on top. The possibilities are ENDLESS.