Yoona and other cast from 'Prime Minister and I' to appear on Happy Together

'Prime Minister and I' cast including SNSD's Yoona re going to be the special guest on December 5th episode of Happy Together.

From the preview photos, Yoona and his leading man actor Lee Beom Soo are sitting next to each other having laughs on the set along with other cast such as Yoon Si-Yoon and Ryu Jin.

What do you think are they laughing about?
Watch Happy Together AT 11:05pm tonight. Meanwhile, "Prime Minister and I' airs its premiere on December 9.