Doctor Mario is just Mario in a doctor suit. He is not a licensed physician, but in the Mushroom Kingdom he's the
finest doc by far. He got his degree by watching House and Scrubs and ER. His motto is "Brightly Colored Pills, they'll cure all your ills! Just as long as you've got Fever or the Chills!" He works with Nurse Toadstool, who is Peach in a Nurse outfit. Figures.
Trust me, Dr.L is better