What is Dr. Mario a doctor of?

[Del Murder]

Please help me.

[Bunny]

Clearly a Urologist.

[VeloZer0]

I'm assuming it is honorary, for saving the Princess so many times.

[Psychotic]

Love.

[NeoCracker]

Strange love, to be specific.

[Hollycat]

He has a doctoral degree in graphology.

[Pike]

Got the Dr. Mario tune in your head? Ready for something that cannot be unheard?

Good.

I am Doctor Mario and I am saving lives
I look different in this game,
(I lost the hat, got a coat, doctor's light, stethoscope)
I am Doctor Mario and I prescribe high fives
Laughter's the best medicine so BAH-HAH-HAH you fell down.

In the Mushroom Kingdom, I'm the finest doc by far
I got my degree by watching House and Scrubs and E.R.
Brightly colored pills! They'll cure all your ills!
Just as long as you've got fever or the chills.

[Jiro]

He's not a doctor or a plumber. He's a gold digger.

[Sephex]

He...uh...he's a doctor of...killing viruses in a very specific manner. I be his copay is too expensive. Especially if you have level 20 viruses or beyond.

[Rantz]

He'll enter your pipes and fix them good.

[Bubba]

I demand to see Dr Mario's credentials. I'm sure there is more to being a doctor than lining up coloured tablets...

[Tigmafuzz]

Mario's a doctor in the same way that Dr. Phil is a doctor. He's not, he just pretends to be so he can make money.

EDIT: Dammit Pike. I thought I had erased that from my memory.
You've got mononucleosis, halitosis, scoliosis, fifteen days is my prognosis
You need red and blue pill doses!
You've got scabies and phlebitis, chronic rabies, hepatitis,
You'll be brave and you'll unite us (then you'll die of menengitis)

[Bunny]

Dr. Phil is totally a doctor. A very, very bad doctor.

[Slothy]

By my count, he's attained his phd in Herpetology, Paleontology and Mycology. He also won numerous track competitions in long distance running, the 100m, and the high and long jumps while studying at various illustrious learning institutions around the world.

Of course he's combined all of these seemingly disparate fields of study into the singular discipline of kicking ass.