Open your canned lychees and drain them well so they aren't sitting in extra syrup. Take a fresh blueberry and press it gently into the hollow center of each lychee, where the pit used to be. If you want a spookier look, thread two finished eyeballs onto a cocktail skewer so they stare out from the glass in pairs.
Lay the finished eyeballs in a single layer on a baking tray and pop them in the freezer for one to two hours, until they're solid. I always do this step because frozen eyeballs double as ice cubes, keeping the punch cold without watering it down as regular ice would.
A few hours before your party, put the pineapple juice, blood orange juice, apple juice, and rum (if using) in the fridge or freezer to get them nice and cold. Cold juice makes for a much more refreshing punch and means you won't need to add extra ice at the last minutes.
When you're ready to serve, pour the pineapple juice, blood orange juice, apple juice, and lime juice into your punch bowl or dispenser. Add the rum now if you're making the adult version, then give everything a good stir so the flavors combine evenly.
Drop your frozen lychee eyeballs straight into the bowl. Some will sink to the bottom while others float on top, which honestly makes the whole thing look even creepier. Ladle it into cups right away so everyone gets a few eyeballs staring back at them.