Group Name: B1A4
Company: WM Entertainment
Number of Members: 5
Intro Video: (with subs)
B1A4 refers to the fact that within the members one is blood type B and the other four are blood type A. It also stands for “Be The One, All For One”. 
B1A4 was introduced through a webtoon.
B1A4’s agency said, “There are a lot of interesting pieces of information about B1A4 in their webtoon,” 
Jinyoung is the leader of B1A4, is blood type A, and was born in 1993.
B1A4’s agency said, ‘“Our agency is receiving a flood of calls asking for more information. Jin Young is the team’s leader and has been trained in composing, singing, and acting for a while now. He’s exceptional in musical talent, and their upcoming album will feature a song composed and written by him.”’  The song he wrote and composed is “Bling Girl”.
Here’s a video of Jinyoung’s profile photoshoot.
Baro is the rapper, is blood type B, and was born in 1993.
“A representative of WM Entertainment, the agency of B1A4, stated, “Unlike his cute looks, Baro actually has a charismatic rap tone. He took over the entire rap making for their debut album, and has exceptional skill talent in that area.’” 
Gongchan is the maknae, is blood type A, and was born in 1994.
“A representative of WM Entertainment stated, “Gongchan is the maknae and the main vocal of the team. He not only has vocal talent, but impressive acting skills as well, so he will be able to promote in a variety of different areas.’” 
Sandeul is the main vocalist, is blood type A, and was born in 1993.
“A representative of WM Entertainment stated, “Sandeul is always smiling, so he makes people feel happy. He’s serious when he sings, though, which is why he’s the member that we all feel deserves to be the main vocalist.”’ 
Sandeul has a really good voice; here’s a video of him singing at a music festival.
He even won a Daesang. (A Daesang is the Golden Disk Awards’ most prestigious award.)
CNU both raps and sings, is blood type A, and was born in 1992, making him the oldest.
I can’t figure out how CNU’s name is supposed to be pronounced. If you pronounce it like a word it ends up sounding really weird because there’s no vowel between the C and the N. If you say it like C.N.U it’s better, so maybe that’s what it is. If you said if fast if sounds like “seein’ you”.
“WM Entertainment stated, “CNU is a health enthusiast. He’s an impressive member with talent in both singing and rapping. CNU’s masculine and a bit on the quiet side, but has a charming smile that captures the hearts of women.”’ 
In 2009 CNU performed at a youth song festival. He’s the one in blue.
On April 21, 2011 they released their mini-album “Let’s Fly”. 
03. 못된 것만 배워서 (Only Learned Bad Things)
04. Bling Girl
05. Only One
06. O.K (Inst.)
On the 25th they released the full music video for their title track “OK”. 
0:32, 1:23 – Sandeul (I think he’s the one singing chorus, he wears yellow shirt)
0:36, 0:43 – Gongchan (the one who sings love me baby and tell me now repeatedly, he wears white)
0:45, 1:49 – Jinyoung (he wears a vest and red shirt)
0:57, 1:04 – CNU (the one with eye glasses and long hair, the one wearing grey shirt)
1:09, 1:35 – Baro (rapper, he wears blue and a hat)
Youtube User: Acinat05
Music Video Bloopers:
B1A4 debuted on Music Core with “OK” on April 23, 2011. 
Here’s the MR removed version:
B1A4 also debuted on M! Countdown, Inkigayo, Music Bank, and Music Core.
This is a video profile of them. Most of it I’ve already covered, but feel free to watch it anyway.
On May 1, 2011 AllKpop.com reviewed B1A4’s mini-album “Let’s Fly”. I’ve picked the parts I found most relevant, but you can read the entire article here. 
“For rookies, B1A4 have two things going for them: solid vocals and a great stage presence. Those two aspects of music are key to succeed, not to mention vital in the world of mainstream music.
B1A4, as most pop groups, has one main vocalist, led by Sandeul, and he’s making quite the impression.
“O.K.” is glowing with the signature elements of a Korean pop song; it has a very average – or – okay arrangement, familiar instrumentation, and the same cheerful texture in the vocals that we’ve heard before, but the pace is very much there and it correlates well with this time of year.
The feel-good vibes of “O.K.” is matched on stage with high energy movements and choreography. During their live performances, B1A4 are literally jumping, running, and laying it all out like it’s nobody’s business. Even more impressive is that Sandeul (main vocalist) is carrying most of the vocals on his shoulders while he’s kicking and flying around with the rest of the gang, and surprisingly, he maintains a balance and control over his voice through the duration of the song. It only caught my attention because he’s singing the majority of the song.
“Let’s Fly” as a mini album is solid, but it lacks that extra push to make it memorable.
Both “Remember” and “못된 것만 배워서” are well sung and well produced, but aren’t as innovative as they could be, especially now when these kinds of songs have been released by previous groups of this same caliber.
The one track that stands out is “Only One.” It’s the slow tempo song on the album, and what is note-worthy about this song is how classic it sounds. There are traces of early 2000s in there and it reminds me of something that Western boy bands of that time would have sung to a crowd of roaring fan girls. It’s a very understated track for the most part, and only showcases a couple power vocals at the climax, yet it soars like a good pop ballad should.
It’s hard to tell where B1A4 will go from here, but what they’ve delivered so far is a well rounded first dose of solid vocals, solid songwriting, and an understood style that is woven through each and every song.
Overall Rating: 3.9/5″
B1A4 had an interview with Osen on May 25th. (Translation from Allkpop.com)
“The group’s rapper, Baro, stated, “It’s been about a month since our debut and there are already fans who recognize us. More people came to our fan signing than we expected, so we were all surprised. We promise to work hard so that we can show the public more of who we are.”
Leader Jinyoung added, “Thanks to our unique group name, fans have given us unique nicknames like ‘paper idols’ and ‘blood idols.’ Apparently, ‘paper idols’ comes from the fact that our name reminds them of A4 papers, and ‘blood idols’ comes from our blood types. We’re satisfied with the nicknames and glad that people are taking an interest in us.”
CNU continued, “Each of us has a different charm. Baro is good at voice imitations and beatboxing, while Sandeul and Jinyoung are good at cooking. Gongchan may seem cool, but he has a lot of aegyo. Baro and I have taken an interest in writing and composing lately, so we’re practicing very hard.”
Overall, the group endured two years of training, which helped foster their relationship as a team.
Main vocalist Sandeul revealed, “At our dorm, we play speed games or bingo together. These days, we’re busy rehearsing when we have free time, but playing games with the other members is one of my biggest joys in life these days outside of training.”
Now that they’ve made a successful debut, what do they hope for in the future?
Maknae Gongchan replied, “I want everyone in our nation to be able to recognize us. I promise to work hard to make that goal come true.”
Jinyoung concluded, “We consider g.o.d. as our mentors. Their music was great and they’re loved for such a long time still. We’re determined to work hard with everything we’re given.”” 
**Last updated May 25, 2011**
**Note: This article will not but updated any further, as it has been over a month since B1A4’s debut.