One of them was the "Incredible" Hulk. He disguised himself as a yeti in only the fifth issue of his introductory comic book series back in 1963.
Here's the story of why he did such a heroic thing (source /editorializing is all mine).
Psst: it's the real reason they call him "Incredible". And now you know...
The villain General Fang took an army to the peaceful principality of Llhasa to conquer it for his Communist regime. Dr. Bruce Banner received Llhasa's distress call and journeyed there as the Hulk to fight Fang. Those are the facts.
Because he desperately wanted to be a hero and have the epithet "Incredible" applied to him, Hulk decided to disguise himself as "the abominable snowman" so as to take advantage of the superstitions of Fang's soldiers. Fang was not fooled, however... He did not believe in the legends of the Yeti, and so "using a 3-D projection of a dragon", he set up a trap for Hulk.
Hulk was an idiot and jumped at the dragon, thinking it real (I guess Hulk has his own superstitions about dragons?) , and so Hulk fell into an electronically-charged cage. Like he does. On weekly basises.
I will end the story there.
Here's the bit of the comic where Hulk is a hero (by disguising himself as a yeti). Interesting factoid of note: this is the only instance in the entire history of Hulk where he acts as a hero. I use the term "hero" loosely here.
Hey, this was # 6 on my Wish List for 2015! Thanks, Santa!