Dr. T. Garden
From the Super Mario Wiki
Dr. T. Garden is a famed scientist, one of the best in the world, and an inhabitant of the oriental city Sayonara; he is also the inventor of the powerful Super Sushi, which can make whoever eats it bigger and stronger.
In The Super Mario Bros. Super Show! episode "Mario Meets Koop-zilla", Mario, Luigi, Toad and Princess Toadstool, wanting to know how King Koopa had attained his new gigantic size, visited Dr. T. Garden for answers. Greeting Mario, Luigi, Toad and Princess Toadstool, Dr. T. Garden revealed to them through the use of his laboratory's hidden camera that King Koopa had become the colossal Koopzilla after breaking into his laboratory and eating Dr. T. Garden's latest and most powerful batch of Super Sushi, destroying Dr. T. Garden's laboratory, which was only recently rebuilt, in the process.
After a failed attempt to capture Koopzilla with a steel net, Mario, Luigi, Toad and Princess Toadstool returned to Dr. T. Garden's laboratory, where they had him create a new batch of Super Sushi for Mario to eat. After Mario ate this Super Sushi, Dr. T. Garden, Toad, Luigi and Princess Toadstool fled from the rapidly crumbling laboratory, which was falling apart due to Mario growing through the roof of it. Eventually, as Mario and Koopzilla engaged in a titanic battle and in his shoddily rebuilt laboratory, Dr. T. Garden created an antidote to Super Sushi, Super Sushi Shrinker, which he gave to Luigi, Toad and Princess Toadstool in a large needle so they could administer it to Koopzilla and shrink him back to his normal size.
After Koopzilla is defeated and shrunk back to normal size, along with Mario, Mario, Luigi, Toad and Princess Toadstool returned to Dr. T. Garden's laboratory, where they were thanked by Dr. T. Garden for driving Koopzilla out of Sayonara. As he thanked Luigi, Toad and Princess Toadstool, Dr. T. Garden noticed Mario eat one of his inventions and he tried to warn Mario not to. Dr. T. Garden's warning came too late, as Mario ate the Shrinking Sukiyaki as Dr. T. Garden called and was shrunk to miniscule size, and informed by Dr. T. Garden that it would take a week for him to return to normal.