Hello! Project Shuffle Unit (ハロー!プロジェクトシャッフルユニット) was the name given to special annual units in Hello! Project composed of mixed members from current major units. Beginning in 2000, Shuffle Units were created for the purpose of shuffling around these members for releases and concerts as well as to promote friendly competition with a season-long collaboration to see which shuffle unit was able to sell the most copies of their single. By 2003, the competition idea was dropped and unit songs were all sold on the same single.
Shuffle Units were generally composed three to a year, included all current members of Hello! Project, and given a "theme" for their groups. The style of each song in a given year was varied; however, the groups all shared the same B-side.
After 2005, the concept of Shuffle Units was abandoned in favor of splitting Hello! Project into Wonderful Hearts and Elder Club due to the size of Hello! Project. These groups were followed by Hello! Project Mobekimasu, an all-member group similar to H.P. All Stars special unit. In recent years, concerts have simply featured random and unofficial shuffling of members.
2000 Shuffle Units
The theme for the 2000 Shuffle Units Akagumi 4, Aoiro 7, and Kiiro 5 was "Colors" ("Red", "Blue", and "Yellow" respectively). The B-side for this years singles was "Hello! no Theme", a pop-song that is now considered Hello! Project's theme song.
Due to the disbanding of T&C Bomber and graduation of some members shortly following the shuffle releases, 4th generation Morning Musume members Ishikawa Rika, Yoshizawa Hitomi, Kago Ai, and Tsuji Nozomi, as well as soloist Maeda Yuki, filled in as alternates during concerts and performances.
2001 Shuffle Units
The theme for the 2001 Shuffle Units 3nin Matsuri, 7nin Matsuri, and 10nin Matsuri was "Festival" ("Cute Festival", "Raggae Festival", and "Traditional Fesitval" respectively). The B-side for this years singles was "Hello! Mata Aou Ne".
2002 Shuffle Units
The theme for the 2002 Shuffle Units Happy♡7, Sexy 8, and Odoru♡11 was "Happy" ("Happy", "Sexy", and "Festival Barbie" respectively). The B-side for this years singles was "Yoku Aru Oyako no Serenade".
2003 Shuffle Units
This is the first year in which all songs by the Shuffle Units were combined into one released single.
2004 Shuffle Unit
For 2004, there were no shuffle units. Instead, all 46 members of Hello! Project joined to form the special unit H.P. All Stars.
2005 Shuffle Units
The last group of shuffle units.
- Iida Kaori is the only Hello! Project member to have been involved in all Shuffle Units as a member of Aoiro 7, 10nin Matsuri, Odoru♡11, 11WATER, H.P. All Stars, and Puripuri Pink.