What GM prototype directly inspired the EV1's design?

The GM prototype that directly inspired the EV1’s design was the GM Impact.

General Motors unveiled the battery-electric Impact concept in 1990. It was developed with aerospace and engineering partners and demonstrated that a purpose-built electric car could combine aerodynamic styling, lightweight construction, and useful performance. Rather than converting an existing gasoline model, GM designed the Impact around electric propulsion.

The Impact became the foundation for the production EV1. GM refined the prototype’s shape, battery systems, electronics, and safety equipment before leasing EV1 cars to customers beginning in 1996. The production car retained the Impact’s distinctive two-seat, low-drag concept, although the final vehicle was engineered for durability and everyday operation.

The Impact is sometimes confused with GM’s other experimental vehicles. The Sunraycer was a solar race car that influenced GM’s electric-vehicle research, while the later Sequel was a fuel-cell concept. Neither was the prototype directly developed into the EV1. The EV1 program ran from 1996 to 1999 and produced one of the most important early modern battery-electric cars from a major automaker.