Homnibus' magic water stick is an object that was used by Peewit and the Smurfs in the Johan And Peewit episode "The Cursed Country". It produces water on whatever ground it strikes when the person with the stick says "alakazam".
In the episode, Homnibus loaned the stick to Sir Johan and Peewit so that they could use it whenever they would need it on their journey to the Smurf Village. Their first actual use was in the desert that Johan, Peewit, and the king had followed Hefty and Smurfette through to reach their forest, but the water produced by the stick in the desert was too salty to drink. Eventually, when they encountered Fafnir the dragon who was being used by his tamer Monulf to capture the Smurfs and make them work in his diamond mine, Papa Smurf used a cutting of the magic stick to make Fafnir breathe out water instead of fire by entering into the belly of the dragon and using the stick there. The main stick itself was eventually returned to Homnibus, but not before Peewit accidentally flooded the king's castle with it.