In the episode where they're testing ways to fool a breathalyzer, every myth they test on-screen is Busted. Of course, there are dozens of alleged techniques to this out there, and they couldn't possibly show them all. Maybe they found one that works, and didn't want to show it on screen, for fear of drunk drivers actually using it...
They showed that you can beat a motion detector with a bedsheet. If this is true, wouldn't that have been cut out as well?
It was probably deemed to impractical to actually be dangerous to use — it fools the motion detector, sure, but it looks ridiculous and will get the attention of anyone with eyes. Plus you'd need both hands to hold it up like Kari did(handicapping you from trying to do what you're breaking in to do), and even trying the Bedsheet Ghost route would leave your freed hands(and eyes, if you cut eyeholes, which you'd likely have to do) as weak spots for a motion detector.
For what it's worth, it's been confirmed that they once discovered an explosive so powerful, and so easy to make, that they destroyed the footage and collectively agreed to never reveal the findings (barring Adam informing DARPA, though he noted that they were probably already aware). Point being that there is precedent for them withholding results that they deem too dangerous to reveal to the public at large.
The myth is always about a man doing it. So in that sense, it is busted.
Also, they pointed out that the requirements to be electrocuted in this way included being crouching practically on the rail. If you reach that point, you're probably trying to get yourself electrocuted, female or male, because (as Adam snarkily demonstrates) no one is going to think "hey, I have to pee, better crouch down directly above this train track". The original (and busted) myth was about this happening accidentally while standing up, which makes a bit more sense, though as they proved it wouldn't result in electrocution.
During the myth that RFID/mind control tags are inserted when you donate blood, a Red Cross doctor points out some Fridge Logic during the episode: If the Red Cross did insert mind control tags, there wouldn't be a blood shortage, since the Red Cross would use the mind control tags to get donors to donate more.
In the test of The Bridge (US) and a woman holding a grenade for two hours, Adam didn't find it as difficult as shown in the episode. However, most men have larger and stronger hands than most women, so this test would probably have been more accurate using a female tester.
However, he also notes that he could tie down the grenade, and it wasn't difficult to hold it with one hand. The woman would've been able to switch hands or call for help. Or, she could've thrown the grenade away herself rather that wait for someone to do it for her. Does anyone know if there was something preventing her from doing that?
If she could have just thrown it away there wouldn't have been a show. However, the clip they play shows the woman being locked inside a small room with boarded-up windows along with her two young children. Not only could she not throw it away, the risk to her kids meant she would also be less likely to even think about experimenting with other ways to keep the handle pressed down (which would also be harder to do with smaller hands).
The "myth" where Adam and Jamie manage to fool the biometric fingerprint scanner. In the summation, they noted that the more "advanced" biometric scanner actually seemed easier to fool than the basic fingerprint scanner. Then I realized that it only seemed that way because, in figuring out how to fool the basic scanner, they'd already done most of the work in figuring out how to fool the more advanced one. Strictly speaking, the biometric scanner probably *was* harder to fool (after all, they did need to lick the latex and paper, a step they didn't need to take with the basic scanner), but not by very much.
The narrator was always fairly present in Myth Busters but he became extremely prominent in later seasons. The show also became more prone to repeating itself and recapping events that already happened, much to fan frustration. Why? In early seasons they covered myths a lot of people had heard of, widely-known tropes, or general concepts most people were already familiar with - These things required little explanation because the audience already knew them. As time went on the myths, tales, and concepts they tested got increasingly obscure and further outside the sphere of cultural awareness, requiring more narration and more recap for a late-comer to know what's going on since they were less likely to recognize it without help.