Let me start off by saying that I mostly agree with Jack. There is a good chance that Ewoks eat people (human people). Why else would they put Luke and Han on those roasting sticks. It sure looks to me like they were going to roast them and then (logical next step) eat them.
Oh, in case you didn’t know. The original plan was to have some super intimidating creature that the Rebels first fear and then team up with. These creatures were going to be the wookiees. When George Lucas started Episode IV, he didn’t know if he would get to the last movie—and he really liked the wookiees. He decided to put one in as Chewbacca. That left the Ewoks in Episode VI. (see The Secret History of Star Wars)
MRE Hot Sauce Bomb
It’s sort of a bomb. Really, it’s supposed to be a type of tear gas. Of course an MRE is a “meal ready to eat”—but it’s even better to eat if you heat it up. Most MREs come with a chemical heater. It’s a small package that gets hot when water is added. Along with getting hot, it also produces a gas. This gas is the source of the bomb. All you need to do is to put the heater and water in an enclosed container and the interior pressure will eventually build up and explode.
For MacGyver’s version, he adds hot sauce. When the water bottle explodes, it spreads hot sauce everywhere. Yes, pepper spray is essentially hot sauce (but very hot hot sauce).
Tire tool slingshot
Really, there’s not much science here. MacGyver uses bungee cords to launch a tire tool (one of those things to remove wheel bolts) at a car. This would pretty much work, but it might be tough to get a good hit.
Jack Heart Pump
The “heart in a box” breaks. Instead of replacing the broken pump with a traditional pump, MacGyver uses Jack’s heart as the pump. It’s sort of funny.
Most generators are just some method to turn an electromagnetic coil to create electricity. You can use wind, water, steam, or yes—a gasoline engine. In this case, MacGyver connects a scooter to the generator. Boom. Power.