Simplify the following text for a Grade 4 native English-speaking person.
Original: Mario has had several other occupations : in the Dr. Mario series of puzzle games , which debuted in 1990 , Mario is portrayed as a medical physician named `` Dr. Mario '' ; in the Game Boy game Mario 's Picross , Mario is an archaeologist ; and in Mario vs. Donkey Kong 2 : March of the Minis , Mario is the president of a profitable toy-making company .
Simplified: In the Dr. Mario games first seen in 1990 , Mario is a doctor . In 2001 , Mario appeared in Dr. Mario 64 , an updated version of the original puzzle game .