The Professor is a character that appears in Sonic Underground. He is an elderly science teacher from Mobius University and used to be one of Sonia the Hedgehog's lecturers while she was studying at the university.
Having stolen what appeared to be two priceless artifacts from Dr. Robotnik at an auction, Sonic and Sonia visited the Professor at Mobius University to see if he could ascertain the location of the lost city of Mobupinchu from one of the artifacts. Manic remained behind to secretly trade the other artifact for cash.
Intrigued, the Professor scanned the object using the Gamma Spectrum Analyzer to find out where it was buried, only to discover that it did not originate from Mobupinchu. The artifact was merely an old Mobian shell case from an ammunition dump. It was only approximately 500 years old and was created during the last Mobian War prior to Robotnik's reign, but Robotnik's archaeology experts did not tell him this for fear of making him angry. The Professor warned Sonic and Sonia that the shell case could explode if it were in better condition, and kept the object in his study after the hedgehogs left the university to tell Manic the news.
Sonia the Hedgehog
The Professor and Sonia seemed to get along very well, as she was regularly praised for asking of tough questions and her inquisitive nature.