This Friday, the hot tub -- the water-logged symbol of free-wheeling hedonism for those that lived through the 70's and 80's -- joins the phonebooth and the DeLorean as one of science-fiction's most unlikely time machines. It transports three high school buddies (played by John Cusack, Craig Robinson, and Rob Corddry) and one of their nephews (Clark Duke) back to a single wild night in 1986. If you're expecting a high-tech explanation for a hot tub that grants the ability to travel through time, then you might want to move along. If, on the other hand, you're looking for drunken sexual hijinks and gross-out laughs, then Hot Tub Time Machine delivers.

That's not to say there's no explanation given at all, just a highly unlikely one. By spilling a banned-in-the-USA Russian energy drink onto the temperature controls, the hot tub can break all the laws of physics and allow those within to travel to whatever time the number for the temperature is set to. Now, to try this at home, pour some Rockstar on your hot tub's control panel and set the temperature to 1,986-degrees.

You will either...

A) Travel through time.
B) Boil to death.

Sci-Fi Squad can not guarantee your safety.

Maybe you've noticed the scene in which the four main characters look at themselves in a mirror and see that they're in the younger, teen bodies, EXCEPT for Clark Duke, because he wasn't born yet. How is that the three main characters have aged backwards while Duke even exists at all? Shouldn't he have evaporated? I also question the scientific authenticity of young Craig Robinson's high-top fade. 1986 would've seen Robinson sporting a gerry curl or something akin to Theo Huxtable's non-descript one-length hair-do, not a hairstyle straight out of House Party 2. Unless Craig Robinson's past self was from the future, I'm not buying it.

Clark Duke does flicker on occasion, when decisions that the three dudes make start to affect whether or not he'll be born half a decade later. The crew know enough about time travel to attempt to do things exactly the same as their first moment on this date, but selfish motives (read: hot sex) cause them to wreak havoc on the timeline. Yes, that means John Cusack is willing to allow a family member to dissipate into nothingness in order to get his rocks off.

The most mind-bending paradox occurs at the end of the film. I'd call this a MASSIVE SPOILER, though the commercials on television pretty much already ruin it. This is the sentence of no return; are you ready?

The group allows Rob Corddry to stay behind in 1986. How can he travel back in time to 1986 if he stayed in 1986? The film paints him as a heavy metal loser, and, by staying back in time and reliving his entire life with the knowledge he has now, he makes a fortune with technological innovations. So, if the new version of Corddry grew to become a rich man, he wouldn't have lived the life that brought him to the hot tub time machine in the first place, thus preventing him from ever becoming a rich man. When Cusack, Duke, and Robinson arrive in the present, Corddry is there to greet them (twenty-four years later) and introduce them to their new lives that they changed by mucking around with the past. If the three of them were gone, how were they able to change their own lives?

Head, explode.