Summon Charms are special items that appear in Kingdom Hearts II. They allow Sora to summon certain allies to help him during his journey. They are obtained after significant story events or found in chests.
Kingdom Hearts II
After Merlin explains about the damage caused to Pooh's book, he gives the Baseball Charm to Sora, explaining, "Simply concentrate on it with all your heart, and you need only to say the word to summon an ally who will help you in time of need." From then, Sora could summon Chicken Little.
After saving Agrabah on his first visit, Sora receives the Lamp Charm, empowering him with Genie.
Sora finds the Ukulele Charm in a chest in Hollow Bastion, binding him to Stitch, who was coincidentally lurking around the world at the time.