Much like there was something about Mary, there is something about sleeper cars. These are the cars that look staid, placid even, but tend to zoom like rockets when the accelerator is floored. And this happens because while not much was done to make the design attractive, there was a lot of thought put to what went under the hood.

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Some of these cars were special trims to otherwise dull models, while some were a sleeper generation in entirety. Whatever be the reason for their awesomeness, these are the 10 sleeper cars of the 90s that we are thankful for.

10 The Better Ford Taurus: Version SHO

The Ford Taurus was just your average commuter car – it was good, economical, and lasted long. But nothing was amazing under the hood of the Taurus, at least not until you bought the 1998 Ford Taurus SHO. The SHO was not a nifty spelling of show but stood for Super High Output. Ford at the time had a surplus of small but really powerful Yamaha engines sitting about with them because the car they were supposed to go into had been canceled before hitting production. So Ford fitted them in the Taurus but the gave this all-new car no different treatment other than SHO lettering on the rear bumper, and some more than 200 horses as the Super High Output.

9 The Stealth Sedan: 1991 Mercedes 500E

The Mercedes-Benz W124 was a cool enough sedan, but when the 500E was launched – its superiority shone through. Today, it may just look like one of those classy old Merc sedans, but with a 5.0-liter V8 engine that jets out 326 horses, it is still as high and mighty as they come.

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It could go 0-60mph in six seconds which is pretty fast for a formal, full-sized sedan as this – and near about as fast as a Ferrari 348. The W124 was a cool enough car, and the 500E looked identical to it except when you floored the pedal and found the monster under the hood.

8 Chevrolet Impala: Generation 7, SuperSport

The seventh generation of the Chevrolet Impala was a limited run of two years, producing the venerable Impala SS – these were back-to-the-board muscle sedans that looked far more submissive than they were. Related to the Chevy Caprice, they bore the powerful LT1 engines under the hood – and yes, LT engines are the ones Chevy lovingly puts into the Corvettes. 260 horses and 330 ft-lb torque took this rather boring and toned-down version of the Impala places, and it went there fast. No one could ever look at this car and ever think power – but this unassuming ride did leave many slack-jawed at traffic signals.

7 Buick Roadmaster: The 1994 LT1 Engine

The original Roadmaster was a 1930s car and one of the biggest things on wheels; that was not a limo. The 1990s rendering of the Roadmaster also had to be large to live up to its 33-year absence, but it sold like hotcakes not because of size alone.

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At its 1991 launch, it came with a 170 horsepower engine, that was revved up to 180 the next year. But it was in 1994 when Buick put in the Vette’s 260-horsepower LT1 engine that the Roadmaster truly mastered the road, though it had to be limited to a 108mph speed lest it reached escape velocity.

6 GMC Syclone: Not The Ideal Truck

While technically a pickup truck, the GMC Syclone was best used to leave opponents slack-jawed in the dust cloud; as it sped away at speeds trucks in the 1990s did not reach. 280 horses propelled this lightweight and compact pickup truck to lightning-like power that let it go 0-60mph in five flat seconds. The all-wheel-drive and the 350 ft-lb torque was partially the cause, as was the Syclone’s light body and a rather compact size. Most saw this as a rather stunted pickup truck that was no good for hauling – but the Syclone’s charm was the power-keg that lay under the hood.

5 1994 Mercury Cougar: Seventh Generation

The Mercury Cougar was all muscle and heart in the early 70s but started to divert once the mid-70s malaise era hit the car market. The 1989 model had a bit off sass, though it still did not look like anything much. Many dubbed it as a luxury if underpowered Mustang while others compared it to the Ford Thunderbird. But with the 1994 engine upgrade to a 4.6-liter SOHC V8 that jetted out 205 horses, the Cougar became one cool sleeper. It did not look like it could overtake a bullock cart, and there are tuned versions of it that have left a Stang in the dust!

4 Volvo 240: Banger Racing At Its Best

Volvo 240 started its journey in the 1970s and ended its long run in the early 90s – but that’s no reason to discount it especially with its latter 90s years being it's very best. While the engines ranged over the years, in America it was mostly the inline-fours that worked in the Volvo’s favor, with modest output horses of 170. However, these cars could be re-tuned well and ran cheap, making them a favorite hand-me-down from cantankerous grandpas to their smirking grandchildren. One push of the pedal and you’d become immediately wiser to the sheer power of the car that looked like it belonged to an archaic car museum.

3 Dodge Neon ACR: 1994 Racing Mopar

The Neon was a cheap and rather ordinary commuter car that no one gave two hoots about unless they had it. Even then, it was no great shakes. But then Dodge sneakily introduced the Neon ACR in 94 with the same looks but with racing Mopar under the hood. The 2.0-liter DOHC twin-cam produced upwards of 150 horsepower and gave this compact, lightweight a car a near racecar-like performance.

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The differences in looks lay in the wheels, as well as the ACR lettering that stood for American Club Racing. The performance, coupled with the name, soon made this one a favorite with amateur and hobby racers.

2 SVT’s Win: Ford F-150 Lightning

The Ford F-150 made for a good pickup – it looked good and could haul as much as you needed, and did so as a comfortable ride. When Ford introduced the SVT Lightning in 1993, it did so with the same looks but a very different under-the-hood configuration. The Ford F-150 Lightning jetted out 240 horses and a 340 ft-lb torque, plus was lighter and differently wired than the Ford F-150. It made for true performance indeed from its 5.8-liter V8. It was slower than the GMC Syclone but could haul the same payload as the slower Ford F-150, normal edition could.

1 The Ultimate: BMW e39 M5

So a sleeper doesn’t always have to be an old and rundown car, as is clear with the last and most powerful entrant on this list – the BMW e39 M5. The looks are cool and classic BMW, but rather unassuming and completely belying the brute power of the car. The 4.9-liter V8 engine lets forth a whopping 400 horses on a rear-wheel-drive that nearly propels the car forward rather than just moving it. 0-60mph was in a super quick and super smooth 4.8 seconds with a maximum speed of 155mph. This was the ultimate for every sleeper car aficionado in the 90s and remains.

NEXT: 10 Classic Muscle Cars That Need To Make A Comeback