For best results, store vodka in freezer. Combine vodka and lime juice in a shaker with ice and shake until cold, about 20 seconds. Strain into a shot glass.
Dip a straw into the Bailey's and put your finger over the end to create suction. Allow one drip at a time to fall into the vodka and lime juice mixture. Then. place the end of the straw into the shot glass and release your finger just enough to allow a strand of Bailey's to come out. Alternate drips with submerged strands until you have something that resembles a brain.