Doctor Who: 20 Things You Didn't Know About The Ninth Doctor
7. He Was The First Doctor To Regenerate While Stood Upright
As well as being the only Doctor to have his regenerations broadcast in reverse order, the Ninth Doctor was also the first Doctor to regenerate while stood in an upright position, something that became the norm from here on out.
Doctors One through Seven all regenerated while either lying down, or, in the case of the Second Doctor, while spinning around in circles and flying towards the middle of the screen. Something weird like that.
Now yes, the War Doctor and the Eighth Doctor also regenerated while stood upright, but these weren't broadcast until after the Ninth Doctor's regeneration in 2005: War's was seen in 2013's The Day Of The Doctor, while Eight's was seen in the short episode The Night Of The Doctor, which aired in that same year.
He doesn't often get the credit for this, but the Ninth Doctor's regeneration kick-started a trend that saw the Tenth, Eleventh and Twelfth Doctors burst into golden flames while standing proud and tall, and presumably, the Thirteenth Doctor will follow suit.