There is no way Dr. Mario has any training. He just throws random pills at the problems hoping that they line up and do something other than cause an overdose.

"Dr." Bubs is in Quadrant III. He's the most quackinest.

How are Oz and Phil so high on this spectrum?

For reference on the no training side:

Dr. Dre and Dr. Venture: Both possess honorary doctorates. The former from UCLA, the latter from a Tijuana community college.
Dr. Pepper: Charles T. Pepper did have a medical doctorate. He is cited as a possible source of the name.
Dr. Evil: Evil medical school.
Zoidberg: Claims he lost it in a volcano, more likely a art history degree.
Dr. Horrible: Likely physics though he claims Horribleness (though it could be a catchphrase.)
Dr. Seuss: Intended to get a Doctorate of Philosophy, got an honorary doctorate of Humane Letters.
The Doctor: Per This - While pretending to be the Doctor in an effort to save herself from an army of Cybermen, one of the planet’s deadliest enemies, in Death in Heaven, Clara said: ‘I don’t even really have a doctorate. Well Glasgow University, but then I accidentally graduated in the wrong century.’
Doc: Does become a doctor at Storybrooke hospital in a live action show, "Once Upon a Time", apparently not a surgeon though.
Spin Doctors: No doctors.

I feel like a fair amount of those on the trained side aren't medical doctors (Phil, Ock, Robotnik, Lector, Honeydew) or at the very least, aren't folks you'd want around for your heart attack.

You're missing Dr. Zhivago, Dr. Kevorkian and Dr. Shipman.

Having The Doctor at the top is a little strange, because hanging with the doctor could very well mean your death, but it will be worth it.

Some unsolicited comments on this:

• I would absolutely trade Dr. Bunsen Honeydew with Dr. Mario.
• The Dr. Pepper position is just pure slander.
• Dr. Horrible and Doogie Howser, MD is the true duality of humanity.
• Zoidberg is suspiciously much higher along the Y-axis than I would personally prefer.
• Dr. Dre, like I would forget, is absolutely a quadrant II candidate. There's just no way I'd put Spin Doctors high along the Y-axis than Dre.

You've got Doc Ock but no Doc Doom?

Isn’t/wasn’t Dr. Strange a surgeon?

You should probably switch Zoidberg with Dr. Pepper.

Dr. Robotnik is more trustworthy than Phil tbh, but I suppose context matters.

Zoidberg should be lower.

Trying to figure out where Dr Doom would fit. Supposedly he does have a doctorate but it came from Latveria so could be a bit... biased

This Dr. Pepper libel will not stand.

NPH making the list TWICE!? Truly we live in the best timeline.

Ah, the late, great Hannibal Lecter.