Namely: why a bus?
Ok, yeah, I can grasp it a little better now. That is a pretty massive Greyhound capable of cruising the U.S.A. at high speeds. If you're thrown under that mother, you're a goner. But can't the same thing be said for any number of large, steel vehicles or other forms of transportation? Maybe we should have a gander.
Thrown under the train.
I love trains. The railroad is one of the things that helped make America great (aside from stealing all the land from Indians and allowing corrupt government officials to get extremely wealthy.) Aside from all that, though, there is very little I enjoy more than the click-clack of a passing train. Love for trains and the adorable picture of Thomas the Tank Engine aside, though, I really don't want to be thrown under one. Just ask this zombie how it feels!
It feels like he got cut in half!
Thrown under the helicopter.
I have a pretty good idea why this one never took hold. If you throw someone under the helicopter, they're probably just gonna have to lay in the grass for a while. That or one of those skis might squish them a little bit. If we're going for the same "squished" effect that makes tossing under a bus such an appropriate parallel for betrayal, I think the right phrase should be "thrown above the helicopter." Not "thrown over the helicopter" because, again, you'd just be landing in the grass. No, with "thrown above the helicopter" you call to mind the effects that four blades spinning very rapidly could have on a human body.
Yeah, probably something like this.
Keep that in mind the next time someone really screws you over, so you can loudly exclaim, "That motherfucker really threw me above the helicopter!"
Thrown under the airplane
An unloaded Boeing 747 weighs a little over 900,000 pounds. That figure right there is enough for me to not get thrown under one. But, to do myself one better, consider that the Boeing 747 goes down the runway at about 180 miles per hour to achieve take off. I got a B- in high school physics, but I'm just going to go ahead and assume that something that heavy going that fast will vaporize a human body, while the pilots casually flip on the plane's giant windshield wipers.
With all this said, I think "thrown under the airplane" should be reserved only for time of particularly self-centered treachery. Like, "That cocksucker almost derailed my plans for the future. He totally threw me under the airplane."
Thrown under the bicycle
This one really isn't that bad at all. I think it should be reserved for the most minor instances of double-crossing, or what I like to call "white back-stabs." Getting thrown under a bicycle wouldn't really be that bad. At worst, you spend a couple weeks in one these bad boys and you'd be good as new.
For an example of how to use it in your everyday parlance, look no further. "Yeah, I told AP that I ate all the Chex mix, but I really just hid it. I feel bad for throwing him under the bicycle."
Thrown under the hovercraft
Like thrown under the airplane, "thrown under the hovercraft" should be reserved for only the most loathsome deception (or loathsome Decepticons). Hovercrafts travel on a cushion of rapidly moving air that is generated by an array of propellors and high-powered engines. If you've ever seen Rumble in the Bronx you know that when a hovercraft drives over a car it sucks all the paint off. And, since we know Jackie Chan would never lie to us, we can assume that anyone thrown under a hovercraft would suffer an unspeakable fate and, most likely, end up in a travelling exhibit.
If you are keen on adding "thrown under the hovercraft" to your vocabulary, the most effective delivery would be, "Fuck you, man. You threw me under the hovercraft."
Hold on, though. I just had a thought that might undo everything I have written above. What if when they originated the phrase "thrown under the bus" they were trying to express the idea of getting thrown under THE Bus?
The only cure for that is one of these.