A Watertown man was arrested early Sunday after he allegedly climbed into the back seat of a stranger’s car in Allston, demanded a ride back to his Watertown home, then damaged the car when the driver refused. According to Boston Police, Pat Malstedt, 23, opened the rear door while the driver was parking his car around 1020 Commonwealth Ave. at about 2:30 a.m. Sunday. Malstedt then allegedly asked the driver for a ride home to Watertown, offering him $100, according to police. The driver allegedly told Malstedt to keep his money and to get out of the car, police said. However, after Malstedt climbed out, he allegedly smashed the passenger side mirror and ran into T. Anthony’s Pizzeria. When police arrived, Malstedt allegedly tried to avoid capture by running through the pizzeria’s kitchen toward the restaurant’s back door. Police caught Malstedt and charged him with willful and malicious destruction of property.