Dr. Toby appears in The Super Mario Bros. Super Show! episode "Super Plant".
Dr. Toby is a somewhat absent-minded, yet friendly doctor, who possesses the superhuman ability to sense whenever a plant is dying. When the basil plant belonging to Mama Mario (which Mario and Luigi were looking after) was dying, Dr. Toby could sense it and came running over to Mario Brothers Plumbing to help.
Dr. Toby presented Mario and Luigi with his experimental Super Plant Growth Formula, which he claimed would be able to save the basil bush, and warned them to follow the instructions before leaving.
At some point later, Dr. Toby was called by Mario, who reported that his plant formula worked, but ended up transforming the basil bush into a Plant Monster that was attacking Luigi. Dr. Toby tried to give Mario some advice over the phone, but had to ultimately return to the basement with an antidote for the formula, which he used to shrink the monster back down to its original basil bush form.
As an apology, Dr. Toby then offered the Mario Bros. his new fast-acting Super Yeast formula to use in their pizza dough, but they quickly refuse his offer.