Corners of the internet reacted with dismay to Ford’s introduction of the Mustang Mach-E electric crossover SUV. But Ford’s history with Mustang is one of experimentation, testing boundaries, and most significantly, of pioneering new market segments.

So the Mach-E is in keeping with those components of what Mustang has meant historically. After considering the longstanding malleability of what “Mustang” means, maybe the question we should be asking when looking at the Mach-E is, “What does SUV mean?”

Click through to see some of the Mustang ‘rules’ Ford has bent or broken over the decades.

Rule #1: Mustangs have the engine in front. 

The 1962 Mustang I, 1967 Mach II and 1993 Mach III concepts all illustrate Ford’s exploration of the idea of a mid-engine sports car Mustang.

(Image source: Ford Motor Co.)

Rule #2: Mustangs have a back seat.

This 1964 clay model shows Ford’s examination of the original Mustang’s lines in a shortened, two-seat version. 

(Image source: Ford Motor Co.)

Rule #3: All Mustangs have two doors.

Ford also looked at squeezing an extra set of doors into the original Mustang to improve rear seat access. 

(Image source: Ford Motor Co.)

Rule #4: Mustangs are sport coupes:

Ford has noodled with station wagon versions of the Mustang, as shown with the 1966 concept (above) and the Mustang III study from the ’70s (below). 

(Image source: Ford Motor Co.)

Rule #5: Mustangs have impractical little trunks.

In 1974, Ford debuted the Mustang II hatchback, with voluminous storage space. 

(Image source: Ford Motor Co.)

Rule #6: Mustangs have two expressive headlight ‘eyes’.

As early as 1971, Ford looked at using hidden pop-up headlights on the Mustang. And the Fox body Mustang of 1979 debuted quad rectangular lights that ran until the car switched to styled aerodynamic lights. 

(Image source: Ford Motor Co.)

Rule #7: Aspirational flagship Mustang models have V8 power.

The Mustang SVO (Special Vehicle Operations) was the pinnacle of the Mustang line from 1984 through this 1986 model, and it featured a turbocharged four-cylinder engine as its powerplant in place of the traditional V8. 

(Image source: Ford Motor Co.)

Rule #8: Mustangs have rear-wheel drive.

As with the move toward turbocharged four-cylinder engines, Ford also wanted to move the Mustang to front-wheel drive. The company developed this contemporary front-drive sport coupe, complete with hidden pop-up headlights, to replace the Fox body Mustang of the 1980s, but ultimately debuted it as the 1989 Ford Probe instead.

 (Image source: Ford Motor Co.)

Rule #9: Mustangs have vertical tri-bar taillights.

In a break from the past, the restyled 1994 Mustang debuted wearing horizontally oriented taillights. Fans revolted, and traditional vertical bars returned in 1995.

 (Image source: Ford Motor Co.)

Rule #10: Mustangs are svelte.

The Mustang fastback of 1971-73 was so porky that it gained the nickname ‘bread van.” If a bread van can be a Mustang, so can a crossover SUV. 

(Image source: Ford Motor Co.)