nerdish was kind enough to ask this and nearly 10 days later, I'm finally answering.
Beast is a kpop idol group that debuted in October of 2009 (coincidentally, the same time as MBLAQ and although the groups are friendly with each other, they're often portrayed as rivals). They originally had the group name B2st (which stood for Boys 2 Search the Top, lawlz) but eventually made Beast official (which stood for Boys of the East Standing Tall, not as funny, but still Koreans and their acronyms.)
The interesting thing about this group is that each member had zero industry success before Beast. Most of them were trainees at other entertainment companies and were either let go or back-burner-ed. A couple members were in dramas that were either cancelled or ignored. Upon Beast's debut, the group received attention when media outlets started calling them "Recycled Materials" idols.
With enough time and hard work, they have become commercial and critical successes, winning many awards, including album of the year ("Fact and Fiction") and song of the year ("Fiction", video below).
[Personally, this is my favorite Beast song.]
Now, personally, I haven't paid much attention to this group. They have a lot of ballads and I don't usually like ballads but I will say their faster songs are usually solid. In fact, my first exposure to Beast (Breathe) is still one of my favorite videos, period.
Last year, they made their comeback with their album, "Midnight Sun" and the lead single, "Beautiful Night". The fandom outrage that ensued kind of ruined Beast for me as well as a good portion of their overseas fans. To be fair, it's their company that's to blame but that doesn't change things.
For this video, the company (Cube entertainment) wanted to ride on the coattails of Big Bang's successful videos, "Bad Boy" and "Blue", and film in New York City. That was unsurprising since those videos cemented Big Bang's first world tour. But what Cube failed to do was integrate the extensive culture and the variety of people in that city. They used the streets of Harlem as a backdrop and tried desperately to make it appear as if Beast fit seamlessly into it (yeah, sure, they'll fit in perfectly, even with their ridiculous clothes). And then Cube posted an ad on craigslist for extras in the performance scene where they specifically asked for "Blonde hair, blue eyes". While they accepted those outside of their requests (because not enough blondes showed up), it still pissed a lot of people off that they were in one of the most culturally diverse cities in the world and the company refused to use that diversity.
What annoyed me about that video/song was the europop sound and auto-tune abuse, but eh. You can watch it here.
In short, I like their faster songs. But their company can suck it.
Edited: I almost forgot to mention that the leader of Beast, Doojoon, is working with Joon of MBLAQ in IRIS 2 that just started airing.