Upon entering the 100 Acre Wood, you'll walk into Winnie the Pooh. Pooh tells Sora that he's looking for his friends and Sora offers to help him. The two set off together in search of Pooh's friends, and now it's mini-game time. Find all of Pooh's friends and use to call him over. The honey at the top-right of the screen is Pooh's energy. If Pooh runs out of honey, he'll doze off for a while, so keep his energy up as you're looking.
Below is a table of where to find Pooh's friends.
When you see Owl perched up in the tree, there should be a batch of balloons around. Call Pooh over to make him ride them up. Owl will notice him and start a conversation.
Walk past Owl to see a small circular opening in the ground. Call Pooh over and he'll jump in. Afterward, he'll rise up by riding balloons with Roo not far behind him.
There will be a beehive near Eeyore. Strike it with your Keyblade and Pooh will retrieve Eeyore's tail. Give the tail to Eeyore and he'll notice Pooh.
Start by calling Pooh over to the wagon full of cabbage that Rabbit is using. When Sora gets on the wagon with Pooh, it will break and Rabbit will notice.
Call Pooh to a tree stump by Tigger and he'll sit on it. Make Sora sit on one as well and Tigger will bounce on over. If he doesn't start a conversation the first time, keep repeating this by sitting on different tree stumps until you get Tigger's full attention.
At the start near Pooh's house, go behind the bushes and call Pooh over to Piglet.
Call Pooh over to Rabbit after talking to him, then get Pooh to eat the honey. Then call Pooh over to Piglet and after the conversation, you'll learn Confuse. Keep moving on by making Pooh eat more honey, and then reach the finish line. After the cutscene, you'll gain a new Summon Card, Bambi. You can now leave the 100 Acre Wood.