Todd St. Mark went out with London Tipton after meeting her in the Tipton Hotel Lobby. Once their eyes met, they instantly fell in love. Todd wants to become a dentist, and he was currently at the Tipton for a dentist convention. His father is Mr. St. Mark, who's hotel business (the St. Mark Hotel) is in competition with the Tipton. It seems that Todd does not like Ilsa, because she is mean and ugly. Todd goes on a date with London in the laundry room (it was the only good place Maddie could get), becuase there is no other available location to go to. The date goes terribly due to Muriel interrupting them all the time.
Later, Todd is seen at the bottom of the Tipton with a bullhorn, reciting her a poem. They arrange to meet at the the masquerade ball. After a while of searching, they find each other and kiss. Also, both London and Todd's fathers do not want them seeing each other, so at the ball he is forced to wear a mask or Ilsa and her dog will find him. In the end, Todd is allowed to go to dentist school because his father wants him away from London. Todd promises London that in 8 years he will make an appointment for London. Additionally, he promised to fix Maddie's overbite.
Most of the time, Todd St. Mark wears fancy clothes due to his family being rich. He is seen in a suit commonly. In addition, Todd has short hair, and is fairly tall for his age. He is of a skinny physique.