The person is the self-proclaimed immortal World Chess Champion (also known as the Immortal 1000), whose games inscribed in stone, dated 1796 were recently
discovered in a random uncle (Mâi Kợk Bỉk)'s house in Hanoi, Vietnam.
One of the 136 games in the WCC of 1796 is 1.e4 c5 2. c3 Nc6 3. d4 cxd4 4. cxd4 d5 5. e5 Bf5 6. g4 Be4 7. f3 Bg6 8. Nc3 e6
9.a3 Qh4+ 10. Ke2 Bc2 11. Qd2 h5 12. h3 Rc8 13. b4 Bb3 14. b5 Nxd4+ 15. Qxd4 Bc5 16. Qf4 Qf2+ 17. Kd3 Bc2# 0-1 (transcribed into Algebraic Notation).
As an
expression, to pull a Mukchug Tantsuldigug is to proclaim that a feat (usually idiotic) that no one but oneself has
accomplished a long time ago is considered being the best in the world.