Having a new doctor raises some interesting ethical and moral questions. How much is left behind after one body dies and the new one is created ?. His body changes new organs ,face ect. What about his mind and "imortal" soul ?. When 11 was dying he told Clara it was important that the new one kept the memories of his previous incarnations. So how much will 12 remember ?. There are a few things every doctor needs to have. He wants to protect and help the innocent. Defend them from all sorts of nasty threats. Plus he gets excited about seeing and experiencing new things. He uses his brain to solve most things not weapons. Unless he really has too or is in a really bad mood. There is also the slightly crazy or maybe not so slightly crazy thing. 11/MS summed it up perfectly in TEH. "Mad man in a blue box". He has even been refered to by his own wife as "psycopath". Moffats other creation BC's Sherlock describes himself as a "high functioning sociopath" a little kinder.PC is going to have lots of fun putting his own mark on the charcter. Looking forward to some shocks ,laughs and maybe a few tears in S8.
. If you think about the eleventh hour this post regeneration period best show's the similarity- he's all stroppy to little Amelia, then proceeds to eat most of what is in her kitchen- typical teenager behavior i'd say. And thinking about it also, most teenager's like to sleep all day, just like tennant's post regeneration state. it's like regeneration is puberty, Then post regeneration he has a brief human teenager like phase (acting weird in various way's like they all have in one way or another until his body and mind change is fully complete) Then when the regeneration is finally sealed and done, that's when he's normal again, the same man, slightly affected in body and mind by the change he's been through.