I nominate the Phantom Time Hypothesis, which maintains that European history had three spurious centuries added to it.
Cyrus Teed’s Hollow Earth theory (we’re living on the inside!). http://en.wikipedia.org/wiki/Cyrus_Teed
Moderator’s Note: How about the theory that the moderator is about to move this thread to IMHO?
Oh, wait, that is true.
I remmber hearing one theory about how a long time ago black people ruled the earth. Then they started f’n around with human genetics despite being warned by their God NOT too.
So as punishment, white people (A result of their genetic experimentation.) took over the earth and enslaved the black man.
It’s been quite some time since I heard this crack pot theory so the details are a little vague. For some reason I think this theory was linked to Muslim faith. I can’t remember why though.
I always thought this would be a good premise for a movie. Not that I believe any of this jibe.
Black holes are portals into other parallel universes (universii?).
The theory that humans began life as asexual women, then somehow their breasts moved down as time progressed to form a man’s testicles.
Ok, perhaps it isn’t so much a theory as it is the product of my friend’s and my sleep-deprived minds.
That sounds a little like Blatvasky’s “Secret Doctrine”.
Sounds something like what the Nation of Islam believes, I think.
There’s a one-man hypothesis called Novagaea that was espoused by a person posting under that name on another message board I frequent; his argument is essentially:
-The moon was once the core of the earth, it was ejected through what is now the Pacific Ocean, leaving a huge scar that all mainstream geologists mistakenly believe is the junction of tectonic plates. This cataclysmic event occurred within human history.
-Despite once containing the moon and now not containing the moon, the earth was once very much smaller, so that the landmasses all joined together seamlessly, wrapping the entire surface of the planet (there was no ocean).
-When the moon was ejected, the earth expanded by means of the crust delaminating, so that, say, the top layer of an entire continent slid over the entire bottom layer, resulting in similarities between various topographical features that are geographically separate.
-The Earth now consists of a thin crust of rock, floating upon, and inflated by a seething mass of gaseous plasma.
-The surface of the moon is constructed of regular rectangular panels, conspicuous to the naked eye.
I’m not sure how these different ideas were ever supposed to form anything like a coherent whole, but that didn’t seem to matter.
Aquatic ape Hypothesis.
Lamarckian evolution. That talents and abilities you, personally, develop become encoded in you genetically and can be passed down.
That seems like a good argument to not have kids for some people.
I live about 10 miles from the Koreshan community. It really is a nice place in the winter, but rather primitive.
This theory is not really in the crackpot category. I have seen in before and I just read the wiki article to refresh.
While it is probably not right, please keep in mind we still know very little about the evolution of man and what we accept as fact is theory and scientific reasoning and a patchy fossil record. The Savanna theory has holes in it also, just less holes.
Keep in mind that 60 years the theory of warm blooded dinosaurs was considered crackpot and now it is possibly the predominate view.
Should I even mention all the new theories on T-Rex alone? 
It is now becoming accepted that T-rex was probably more of a scavenger/opportunist than a hunter/predator with comparisons to the modern lion which has had it general perception change over the last century also.
They also now think some if not all of the Tyrannosaurs had feather like covering.
So keep an open mind of the Aquatic ape theory, it just might be partially correct.
Some minor links
Sci-Am article
Plenty of great kooky theories archived here. Includes Francis E. Dec’s “Computer God Parroting Puppet Gangster Slaves”, the theory that Nixon, Reagan, and Stephen King conspired to kill John Lennon, and much more.
Another favorite of mine is Professor Arnold Ehret, who lived around the turn of the century and advocated “mucusless eating” as the path to ideal health. Basically, eat lots of cherries and grapes, apparently. “Every disease is constipation!”
Venus was once part of Jupiter, and broke off. It got its reverse rotation when it passed within 500 miles of Earth. This also accounts for every disaster told about in the Bible. (And yet, the fact of an enormous planet filling every inch of the sky managed to escape mention.)
An April 1 issue of Omni magazine once printed an article about “static gravity” - I don’t remember all the details but the basic idea was that the effect on gravity on a body in motion diminishes in proportion to the speed of the body’s perpendicular motion. They had several examples of observed phenomena that were explained by this theory.
Different to the above theories, but this one I think is coolest because it feels so much like it aught to be true.
The theory that the British rude finger sign of showing two fingers comes from the time of Agincort when archers would show their two fingers to prove they were able to use their bows. And the accompanying beleif that if a Brit was captured by the French their middle and index finger would be cut off to stop them ever using a bow again.
That theory goes hand in hand with the UL that Pluck Yew was the origin of F_ck You. 