http://gearholder.tumblr.com/post/126534577882/i-have-no-idea-what-that-means

There, I found it - 3-

Lemme just fix that last part for this context:

“Basically it means “you (the cabrón) are stupid for thinking [thing] can’t (or shouldn’t) happen (it happens “a huevo”)” but it’s not necessarily aimed at a person and can be uttered to express disdain towards… god? destiny?… when the circumstances make it look like it can’t happend but it do.”

Also when a person asks you a thing and you want to convey a strong affirmative response. In essence a “fuck yeah!”

C’mon, things that are made “a huevo” defy destiny, they gotta amout for something in regards to assurance of fact - .-