Occurence: The Incredible Hulk #79

The Hulk is on an island where Nightmare is manipulating reality and turning Mindless Ones into other creatures, one of those being Fin Fang Foom. The dragon tries to convince the Hulk that he will rule the planet and that the Hulk should kneel before him. The Hulk doesn't budge so Foom breathes his fire on him and it barely singes the Hulk. Foom is amazed at this fact.

Hulk's Physical Resistance Feats

Incredible Feats of the Hulk Main Page