Crane games are very popular in Japan, although they can be found all around the world. You try to grab toys using a remote-controlled claw. You can keep anything you drop into the chute.
In this anime, asteroids are heading for the Earth and our only hope is three schoolgirls playing crane games. It has to be those three. No one else on the planet will do. If all three learn a new technique for getting a toy into the chute, an energy beam shoots out of their heads and knocks away some asteroids.
The show's budget is so cheap that the same "knocking away some asteroids" footage gets reused every week, implying that the same asteroids keep coming back to rejoin their formation. However this might be cunning foreshadowing, since we'll learn towards the end of the series that the asteroids are being sent by Dark Gorilla. (No, I'm being flippant. Of course it's just the lack of budget. The animation is godawful. It's been done in Flash, or something similar, and these are actually just brief animated segments in a live-action TV show of girls playing crane games.)
However the girls haven't realised they're saving the world. They think they're training to become idols. They were a bit puzzled in the first couple of episodes about how playing crane games could help you become an idol. However Agent Fox explained it to them and now they're happily working for their dream! This sustains six repetitive episodes. Halfway through the show, though, they realise that the Earth is going to be destroyed by asteroids and that what they were doing wasn't idol training at all! They were trying to save billions of people and the entire world from obliteration!
"It has to be you," says Agent Fox. "The size of your desire to become idols and the purity of your hearts. You have both of those things together, which is why you can save the Earth."
"I'm going home!" says Mirai. "I don't get it at all! I just want to be an idol!"
"If the Earth's going to be destroyed," says Kyouko, "I want to be with my family." You know, instead of trying to talk some sense into Mirai.
They both leave. Asuka's the only one left. She doesn't say anything bad about her friends, but just says it's their boss's fault for lying to them about becoming idols. Fortunately, though, everyone comes back in the next episode. They even talk around Mirai, the girl who's raised stupidity to the level of planet-busting armageddon.
"I don't care what happens to the Earth! I just wanted to be an idol!"
"Don't think about difficult things," says Kyouko. (The English subtitles water this down to "let's stop trying to think so hard about this", but I'm not deaf.) "Let's become idols together!"
This show probably sounds like a must-watch, but unfortunately it's duller than it sounds. It's not taking the piss out of its heroines. It doesn't seem to have an opinion on their planet-threatening strop and indeed Season 2 is going to have longer, more idol-focused episodes. (Yes, there's a Season 2.) There's a modicum of characterisation, but not enough for anyone to come alive noticeably as a person. Mirai's rich, Kyouko's poor with lots of siblings and Asuka's dad is a fisherman. Mind you, it won't have helped that the animation is so super-cheap and that the voice cast have almost no experience. The only one with any kind of CV is Sora Tokui and even she hasn't been around for long.
It's the kind of show that's funnier to discuss than to watch. The actual episodes are too repetitive and trivial. What's more, they really are teaching you crane game techniques, which is different but not very interesting. I don't mind the Flash animation, which simply is what it is, but it's so cheap that it even fails when trying to deliver mild fanservice (Agent Fox's cleavage or the onsen episode). Its insanity (especially eps.7-8) is the only reason to consider watching it, but it's not a strong reason and feel free to skip a few episodes if you do.