Originally Posted by Shino'sDad
Remember that the Uchiha received the Eyes of the Sage of Six Paths, while the Senju received the Body of the Sage of Six Paths. So it makes sense that there be some sort of special form the Senju can take. I assume that Tsunade's Miotic Regeneration is a lessened form of the First's Form. Madara even mentions that her version is much weaker than Hashirama's when they were fighting, so this wasn't a complete pull out of no where. We were informed he had some sort of special form already.
So, Tsunade's basically an Imperfect "Wood" Sage, while The First is a Perfect "Wood" Sage?
What if similar to Ginkaku and Kinkaku, the body of the Sage was influenced by the Ten tails' chakra, , his sons gained some of this too? Or something like that...I mean, Naruto had his whiskers before he had the Nine-Tails trapped in him due to Kushina being the Jinchurki at that time... Just guessin'.