Here is how Yuna met Gollum, Curing Smeagol's mind and Playing a Game of Riddles goes in Yuna's Unexpected Journey.
Meanwhile at Canterlot.
Human Twilight Sparkle: I hope they're okay, Isamu, Indy and Ann really missed Yuna and her friends.
Princess Luna: So do we.
Princess Celestia: (looked at her foals on her hooves) It's okay, My little ones, You're cousin will do fine.
In the dark pit.
Princess Yuna: Where am I?
Gollum/Smeagol: (singing) The Rock and Pool, Was nice and Cool, So Juicily Sweet! My only wish, To catch a fish, So Juicily Sweet!
Princess Yuna: Gollum? I thought he burned into the lava at Mt. Doom.
Gollum: Aaahh. Is it tasty? Is it scrumptious? Gollum. Gollum.
Princess Yuna: (use her magic for make light) Stay back! Don’t come any closer!
Princess Yuna: Your mind was poisoned, I think I have just the spell for it. (use her magic to cure Smeagol's mind)
Gollum/Smeagol: What's it doing to us? Gollum. Gollum.
Princess Yuna: Gotta keep going! (using her magic)
Smeagol: What happened?
Princess Yuna: Your mind is cured, Smeagol.
Smeagol: How can Smeagol ever repay good ponieses?
Princess Yuna: I'm Princess Yuna.
Smeagol: Princesses, What can Smeagol do in return for Princesses?
Princess Yuna: Can you show me a way out?
Smeagol: Games? We loves games, doesn’t we, Precious? Does it like games? Does it? Does it? Does it like to play?
Princess Yuna: Alright, We'll play a game of riddles and if I win, you show me the way out.
Smeagol: Yes, And If Princesses loses, we keeps it and lets her go alone.
Princess Yuna: Fair enough.
Smeagol: Well, Princess first.
Later, Yuna and Smeagol played a game of riddles.
Princess Yuna: Let's begin.
Smeagol: Why can't anyones jump higher than mountains?
Princess Yuna: Because mountains don't jump.
Smeagol: Very clever, Guess another riddle. Why does one pony throw a clock out window?
Princess Yuna: To see time flies.
Princess Yuna: My turn to pick a riddle. Which test is the Wizard's favorite in school?
Smeagol: We gives up.
Princess Yuna: A Spelling Test.
Smeagol: Very clever riddles. Smeagol must show the way out.
Princess Yuna: Thank you.
Smeagol: Fallow me.