SEE ALSO: Seolhyun shares heartwarming moment with youngest fan in Gangneung

On this day, Taeyeon came live on the air to introduce fans to her new pet dog, as well as to communicate with fans. But during the broadcast, Taeyeon got a big surprise when another celebrity - AOA's Seolhyun - appeared in the comments!

Seolhyun commented, "Unnie why are you so pretty?" Taeyeon recognized Seolhyun SNS ID and remarked, "It's Seolhyun! I saw your movie just now." 

Taeyeon continued by cheering for Seolhyun with, "'Memoire of a Murderer'. I watched it yesterday before bed and I watched it again today. [Seolhyun] did a great job of feeling endangered." Seolhyun appeared as the female lead in 'Memoire of a Murderer', a film released last September. 

But Seolhyun poked fun at Taeyeon with, "You fell asleep while watching it, didn't you!", to which Taeyeon could not lie. She answered, "This unnie can't lie. I have a habit of falling asleep right at midnight. Today, I managed to get to the end. I watched until the name of the sushi chef's daughter." 

Did you know these two were close friends? Check out Taeyeon's full live above.