The energy required to flip the earth's axis is incredible. There is absolutely NO evidence this has happened - ever. True Polar Wander, another unrelated theory is often confused by pole shift advocates.

Mastodons lived in the sub-siberian region and even farther north prior to the last glacial maximum (LGM) when conditions on the planet were generally warmer than they are today. Many carcasses found today actually predate the LGM. Further, like todays modern elephants, the stomach contents of mastodons digest very slowly. There is no need to hypothesize flash freezing to explain the material found in mastodon abdomens. If the mastodons were flash frozen, their carcasses would be well preserved, but this also is not the case. Inspite of some who claim edible mastodon flesh has been found, it is not true. The flesh is found to be in advanced stages of decay.

The idea of the rogue planet (or brown dwarf now) Nibiru in a highly elliptical orbit is based on a poorly researched work by Zachariah Sitchin which has been completed refuted. http://www.sitchiniswrong.com/