01 - In a mixing bowl, combine lime-flavored gelatin powder with boiling water and stir thoroughly with a whisk for approximately 2 minutes until fully dissolved.
02 - Add cold water and vodka to the dissolved gelatin. Stir until well incorporated.
03 - Evenly divide gelatin mixture among 12 shot glasses or small cups, filling each about two-thirds full.
04 - Transfer the filled glasses to the refrigerator and chill for 45 to 60 minutes until the gelatin is just beginning to set but remains tacky to the touch.
05 - Gently press one maraschino cherry into the center of each shot glass so it is slightly submerged in the gelatin.
06 - Carefully pour about 1 teaspoon of Irish cream liqueur over each cherry. This will produce a cloudy brain effect as it disperses into the gelatin.
07 - Return shot glasses to the refrigerator and chill for a minimum of 2 hours until the gelatin is fully set.
08 - Immediately before serving, drizzle a few drops of grenadine syrup over each shot to create a bloody visual.