become a mob with mob behaviours

scoreboard players set @a creeper 2 {Inventory:[{id:minecraft:skull,Slot:103b,Damage:4s}]}
scoreboard players remove @a[score_creeper_min=1] creeper 1
give @a[score_potion_min=0]

scoreboard players set @a cpotion 2 {Inventory:[{id:minecraft:potion,Damage:4s}]}
scoreboard players remove @a[score_potion_min=1] potion 1
give @a[score_potion_min=0,score_potion=0] minecraft:potion 1 4