Answer by taking a quote from the following article:

Wonder Girls (Hangul: weondeogeolseu) was a South Korean girl group formed by JYP Entertainment. The group's final line-up consisted of Yubin, Yeeun, Sunmi and Hyerim. Members Sunye and Sohee officially left the group in 2015, while Hyuna left in late 2007. They were co-managed in the United States by Creative Artists Agency.

After Park Jin-young revealed the name of his first girl group Wonder Girls in May 2006, the Wonder Girls were introduced through a TV show titled MTV Wonder Girls. The first four episodes outlined the characteristics and profiles of each member. Shortly after selecting Yeeun as the fifth member, the Wonder Girls held their first showcase in the MTV Studio. They performed a cover version of "Don't Cha" by the Pussycat Dolls as well as original songs, including "Irony" and "mianhan maeum" ("It's Not Love"). Sunye sang her version of Destiny's Child's "Stand Up for Love", while Hyuna performed a showcase of her dancing skills. The other three members--Yeeun, Sunmi and Sohee--performed a cover version of Janet Jackson's "Together Again".  The Wonder Girls officially debuted in early 2007 on MBC's Show! Music Core, performing "Irony", the hip-hop single from their first album, The Wonder Begins. The album sold 11,454 physical copies in 2007. Shortly after, "Wonderfuls", the official Wonder Girls fanclub, was established. The group held several showcases in China after receiving Chinese lessons. In mid-2007, however, members of the Wonder Girls were beset by various injuries and health problems. On June 25, Sohee was sidelined for a month after tearing a knee ligament in a fall from a running motorcycle during the filming of her movie, ddeugeoun geosi joha (I Like It Hot).  The remaining four members continued performing until late July, when Hyuna was withdrawn from the group by her parents due to their concern over her problems with chronic gastroenteritis and fainting spells. In autumn 2007, the talent agency Good Entertainment sent their trainee Yubin to JYP Entertainment as a replacement for Hyuna. She made her debut three days later in the group's live performance of "Tell Me" on Music Bank.  Their first full-length album, The Wonder Years, was released the following week with "Tell Me" as the lead single. Due to the last-minute addition of Yubin, the album version does not contain her part. However, the performance version of the song was reworked to include a bridge with rapping by Yubin. The single was a hit and reached number one on various Korean television and internet music charts, including KBS's Music Bank. The song also became a number one hit in Thailand. The choreography for the song was simple and widely imitated: by October, many fan performances of the dance circulated on video sharing sites such as YouTube and Daum, including one by a group of policemen who were eventually profiled on SBS's Star King. The dance's popularity was immense and the explosive attention it received became widely known as the "Tell Me Virus", earning the group the title of "Nation's Little Sisters". The Wonder Girls had an extensive promotional schedule for their album, and in late 2007 they began performing their second single, "i babo" ("This Fool"). MTV also began broadcasting The Wonder Life, a reality TV series starring the girls.

What were some highlights of 2006 and 2007?
May 2006, the Wonder Girls were introduced through a TV show titled MTV Wonder Girls.