HaHa left a sweet birthday message for his longtime friend and 'Running Man' cast member Kim Jong Kook.

Kim Jong Kook celebrated his 44th birthday on April 25, and HaHa had a special message for his friend of 10 years. Along with a photo of Kim Jong Kook with his son Dream, HaHa wrote:

"Our Kook hyung, I sincerely congratulate you on your birthday! We've gone through a lot together in our long relationship. We've laughed and cried, and I sincerely hope we can have only happiness in our blueprint of the future! Our dependable and charismatic hyung! Please continue to stay by my side! Your loyalty knows no bounds! I'm learning a lot! 2020 is lonely, and difficult knows no bounds! I'm learning a lot! 2020 is lonely and difficult, but we'll come together and overcome it! I have too much to say... I will hold back! No more words are needed! Hyung! I love you! Stay healthy! From Donghoon."

Kim Jong Kook responded, "Haha. I remember this day. Wasn't this the day I decided to invest? Haha, thanks for the congratulations. 401! Fighting! Haha."

Happy birthday to Kim Jong Kook!