My cat Raisen loves those carrier bags. She sleeps on them, likes to attack INTO them (and lie down), and plays with them. She even loves for me to hold the bag open and pick her up in it. She likes to watch things in the sky move by out the top, I guess. I dunno. (See her here.) I guess she finds the sound fun when active, and comforting when tired.
She's also got her head caught in the handle before and it was no problem for her. She knows how to back out of it. They're not exactly "tight" and backing out is easy after all. But then, having worn collars, harnesses, and used to being on leashes, this is probably not something considered "out of the normal" to her. So she doesn't panic.
If people are worried about the handles, you can cut them off, and leave just the bag part for the cats to sleep on, play with, or whatever.
If this happens to the cat, don't rush around the house after it yelling or making a big fuss because you could end up making the experience far worse and the cats will forever be paranoid of that object - whatever it is - from then on. Cat 1 is already in a panic, the rest of the cats race to see what is going on, all of them see you running around the house, chasing Cat 1, yelling worried screams, rushing around obviously far faster and far more urgently than normal. So they put 2 and 2 together and assume this is a dangerous operation going on. The tiniest things, too, can become a cat's worst nightmare encounter without much effort at all.
Some lessons in this that I've learned by experience, myself...
Sound pretty real? One of my hyper ADHD neices did this once to Raisen when she was smaller, and I had to go through that. Its terrifying for both you and the cat.
Raisen was scared of rubber bands for a while, but I've been successful at teaching her they're not something to worry about. Now, she's constantly trying to paw one down from my desk to play with, and I'm left realizing that now I have to teach her not to play with rubber bands for a different reason. Sigh. So I don't make rubber bands available. They're either used, or in the desk drawer, out of the way of paws and little hands.
However, you NEVER run, make loud noises, curse, or do anything that might increase the panic levels around cats. You can make a cat far more paranoid of everything very easily by your actions, if you're not careful.
Raisen is usually pretty calm, cool, collected, and reasonable in the face of most sudden ongoings. She can handle most anything. Nothing bothers her. But turn on that electric razor...
I don't use it without first shooing Raisen out and closing the bathroom door, now. That's a life-long paranoia that will remain with her, apparently. Sigh.
Anyway, for this reason, when the cats get scared of something now (rarely), I deliberately withhold any signs of fear in myself. Because the first thing they do do is look at you for a reaction...with wide eyes -- in case you seem to indicate "flight" is warranted. If you use the usual calm and soothing "voice" that you use with them all the time during these situations, and move without "urgency" -- while still perhaps frightened, they're usually too busy trying to figure out why you're not panicking to run or panic right away. After all, they're curious about everything, and want to know what you're thinking/doing all the time.
So, if I drop, say, a Nerf Ball on kitty's head, rather than scream "OH MY GOD! I'M SO SORRY! YOU POOR THING! GOD! LEM'ME GET THE FIRST-AID KIT FOR YOU!", I simply bend down slowly, and while looking away, as if nothing really bad just happened. And while my hand is down, I give kitty a quick, tiny scritch behind the ears, then pick up the Nerf Ball and put it away, and make no further fuss. I continue what I was originally doing and ignore her. This way, instead of running away, Kitty instead stays, while giving you a really nasty, but quick, look of "Watch it, you stoopid, silly CLOD!", and then she continues cleaning her toes. But she's not afraid of the Nerf Ball. (If you're wondering how the Nerf Ball was in the vicinity of the poor, hapless kitty, and how it ended up landing upon poor, hapless kitty's head in the first place...well...I plead the Fifth. I will not answer on the grounds that anything I might say may be used against me.)