Nobody is arguing that it’s not mockery, but what are it’s origins? You can do all sorts of things behind peoples heads, why the “bunny ears”?
In Spanish the version with two fingers making a V is “orejas de burro,” donkey ears. The version with the index and little finger is horns, and you reaaaaaally don’t want to get caught doing it as it can lead to broken noses (it’s equivalent to calling the person either a cornudo, cuckolded, or a cabrón, a man who pimps his own wife).
Yes. In Mexico, just called “cuernos” (horns), but somehow constitutes an accusation of cuckoldry. Some Mexican friends were very surprised that this was not the tradition in the U.S.
“Rabbiting,” so I have always heard, is Cockney rhyming slang. “Rabbit and pork”: talk.
I doubt that it has anything to do with the gesture in question.
People do make gun signs at cameras. But it’s not a very family-friendly gesture. How would you make moose antlers? People do bunny ears because it’s easy and mildly funny, that’s it really.
I think you’re thinking about this a bit too hard. 
Easy: thumbs to temples, fingers spread pointing upwards. Can be done to self, or to another from behind. (The junior high we went to was creative.)
I still think it would be fun to discover the history of it, just like we would pieces of language. You know, find the earliest instance. See if you can find someone historically famous who had it done to them and got mad. “This abysmal practice of, while sitting for a photograph, facetiously accusing one’s acquaintance of being of leporidan decent.” Or something like that!
I think your brushing off a potentially interesting answer. Where does this custom come from? When did it start? Noone has addressed this. Just saying, “It’s supposed to be funny, that’s all” isn’t answering the question at all.
In Germany, it has been common for at least 30 years. It’s usually children who do that, because it is regarded as childish.
The fingers represent donkey ears, not rabbit ears, and are thus a childish insult that the other person is dumb. A rabbit isn’t an insult.
I can’t think of other gestures you can do easily and unnoticed - a gun to the head is dangerous and bad, not mocking (guns are bad in our culture). And antlers aren’t insulting.
As for devil horns/ cuckold: While we do have an older figure of speech that a husband who was cheated has been “horned”, it’s not a widespread finger gesture, and it wouldn’t be used by kids against each other, because it wouldn’t fit.
Put your elbows together.
This places your forearms parallel to each other.
Keeping your hands together at the bottom of the thumbs, fan out your fingers. MOOSE HORNS! For added reality, you can bend your fingers a bit.
We were creative, too. 
Nononono.
Nonono.
It’s just a peace sign. Why are you overcomplicating things?
Whence the accusations of overcomplication? As far as I can tell, the only “complication” is suggesting “this gesture has an origin.” Otherwise, we’re just collecting data. Where do the complications arise? It seems like people are suggesting that the subject matter is unworthy of intellectual investigation, which is strange to me. So at the risk of superhyperovercomplicating:
Synchronic interpretations of the mockery gesture so far are:
- Rabbit ears
- Donkey ears (Germany and Spain)
- Devil horns
Context: Usually done by children; usually (but not always) done for photos.
it’s identical in form to the peace sign, but that origin appears to be separate and later. The Japanese custom seems to have a more recent origin, derived from Western culture.
#3 is interesting because, as Nava mentioned, the “horns” (cuernos)gesture in Mediterranean countries and in their sphere of influence is strongly (and anciently) associated with cuckoldry. There’s quite a lot of scholarship on that: the competing theories are that it’s associated with the former practice grafting spurs onto capons, or else the symbolic association with billy goats. Nevertheless, that is one tie-in to support the theory mentioned by Zsofia, that the gesture’s origin comes from the common “horns” gesture. We know that the horns = cuckoldry was formerly well known in the English-speaking world (used extensively in Shakespeare and Marlowe, f’r instance), so we know that there’s a possibility that English-speakers had a gesture for it. Also, the two are connected in their meaning of mockery: strong and serious mockery for the cuckoldry, weak and teasing mockery for the bunny ears.
My slang dictionary suggests that “to rabbit” does derive from rhyming slang rabbit-and-pork = talk, and dates to the 1940s; the gesture predates that, so though it can’t be the origin of the gesture it could be the origin of the gesture as “rabbit ears.”
No conclusions yet, only hypotheses.
I will add one more thought, and it’s almost certainly unrelated:
In a number of old WB cartoons, after one of the characters did something really stupid, they would look at the camera, and for a brief moment have donkey ears (as if to say, “I just made an ass of myself”).
Could you please explain to me why rabbit ears would be an insult, though? Or why children thought them funny?
But when kids do this, do they know that they are calling each other cuckolded? When at the age of around 10 years I called my fellow class-mates names like Son of a bitch (Hurensohn), I knew what it meant (though I didn’t know why it should be offensive compared to other insults - I could only come up with defending the mother, not your own honour), or Masturbator (Wichser), I knew it was an insult (although I only found out much later that people used to believe that masturbating shrank your brain, turning you into an idiot).
Thanks so much. I was going crazy in this thread. I never heard of this “bunny ears” business. Everyone knows it is devil’s horns!
Any chance you’re from NJ?
In Spain 2 and 3 are different gestures.
And yes, when a 10yo Spaniard does #3 to a classmate, he knows he’s calling the classmate a cabrón; he may not know the whole definition (a man who pimps his own women, usually his wife), but he knows it’s sexual, nasty and a reason for blows. #2 is cause for mild irritation at most.
Of the three possible interpretations of the gesture (ass, devil, rabbit), “ass” seems the mostly likely to be at the root of it. “Devil horns” is a different gesture, well known, and it seems likely that the regions that know the gesture as “devil horns” borrowed the name from the better-known cuernos (which has equivalents in Italian, Portuguese, French, etc.). I’d suggest “ass” is older because (1) we have a cross-linguistic evidence that the gesture is interpreted as an ass, whereas “rabbit” seems limited to English; (2) there is a venerable tradition of schoolyard mockery where someone is called an “ass.” (3) The story of King Midas having ass’s ears was once fairly well known. I might guess that “rabbit ears” came into vogue in the English-speaking world after the advent of Playboy magazine, but without dates it’s a wild guess. It could also be because the gesture means “rabbit” in the gesture-song “Little Bunny Foo-Foo.” Who knows.
No. I know of no evidence that children themselves make the connection, and we haven’t even established that there is a connection, we’ve only suggested it. The more I think about it, the more I think that it’s unlikely. I think you and Nava and Earl Snake-Hips Tucker are right, that it’s a representation of “you’re a [silly / stubborn / stupid / inferior] ass, as symbolized by these ears.” If only I could find evidence!
Just to muddy the waters:
Douglas Bruster, “The Horn of Plenty: Cuckoldry and Capital in the Drama of the Age of Shakespeare,” Studies in English Literature 1500–1900 32 (Spring, 1990), 201.