Simone married Gordon Trümper, the guitarist from German rock band Fatun on 1 August 2009, after dating for 12 years.

The four continued to perform, but aside from being featured on a small-time German news program somewhere between late 2002 and early 2003, Devilish were not going anywhere until Kaulitz auditioned on the reality TV talent show "Star Search."

This continued until 2005 when Jost arranged a meeting between the band and Universal Music Group's Interscope Records and Tokio Hotel was signed.

On stage, Kaulitz was noted and well known for his energetic style and harmonizing with the fans (he would frequently let the audience sing verses instead of him).

To support the release of Zimmer 483, Tokio Hotel began a continental tour of Europe, spawning another live DVD and a large publicity boost.

Scream was moderately successful internationally, and to support the release, Tokio Hotel left Europe for the first time in their careers, and flew to the United States.

In February 2008, Tokio Hotel first set foot in North America to play five shows, starting in Canada and ending in New York.

The 1000 Hotels Tour began in Brussels, Belgium, on 3 March 2008, and was set to continue through the Netherlands, Luxembourg, France, Spain, Portugal, Italy, and Scandinavia, ending on 9 April.

However eleven days after the start of the tour, on 14 March, Kaulitz began to experience voice problems in the middle of a show in Marseille, France.

They explained that Kaulitz was sick and was being flown back to Germany to see a specialist: he had played forty-three shows without a break and had developed an untreated throat infection.

Humanoid was released on 6 October 2009, and just short of a month later Tokio Hotel picked up the "Best Group" award at the EMAs in Berlin on 5 November.

Kaulitz wrote his first autobiography, "Career Suicide: Meine ersten dreißig Jahre" ("My first thirty years"), which was written in German, and was due for release on 4 January 2021,[11] however this was pushed back to 1 February 2021.

Kaulitz announced on 11 January 2021 via Tokio Hotel's official Facebook and Instagram accounts their new single "White Lies", which will feature a guest appearance from German EDM duo VIZE.

Other 2021 releases by Tokio Hotel include The Who cover "Behind Blue Eyes"; also with VIZE in May, "Sorry Not Sorry" with German rapper Badchieff in August, and "Here Comes the Night" in October.

Tokio Hotel announced their new single "Bad Love", which was originally to be released on 21 January 2022, but was postponed due to Bill and Tom Kaulitz being unable to arrive in Germany in time for the promotion.

This was eventually released on 4 February 2022 with new singles "HIM", "When We Were Younger", "Fahr mit mir (4x4)" with Kraftklub and "Happy People" with Daði Freyr following on 8 April 2022, 27 May 2022, 8 July 2022 and 21 October 2022 respectively.

[14] In 2022, Kaulitz created a subscription-based OnlyFans account, with proceeds from the subscriptions being donated to the International Marine Mammal Project.

[15] Kaulitz and his identical twin brother, Tom, used to live in Hamburg but moved to Los Angeles in October 2010 in response to an incident involving stalkers and a robbery.

[17] German site dw-world.com says that Kaulitz's look, young age and edgy hairstyle has helped him obtain icon status among many teenage girls.

[22] He cites his fashion and style influences as David Bowie (particularly in the 1986 film Labyrinth), Nena, Vampires, Paris' secondhand shops, striking jewelry and Dior Homme.

Kaulitz was 19 when the likeness was made, making him the youngest person to be duplicated by the Madame Tussauds museum in Berlin.

[29] In September 2009, Kaulitz was chosen by fashion legend Karl Lagerfeld to take part in a photo shoot for the 30th birthday of Vogue in Germany.

[22][30] Karl Lagerfeld described him as "The Other Idea of a German" and wrote that the 20-year-old singer with the unusual styling became a superstar; and a fashion icon.

Designer Michael Michalsky supported his decision by saying: "Bill Kaulitz is unique and uncompromising, Pop-Art brought to life.