Throughout the series in both the anime and the manga, the Host Club regularly engages in cosplay, which is wearing costumes to resemble particular characters from well-known pop media sources. They also conduct events with "themes" and/or host events in which they wear special, or matching, garb. Some of these thematic events include:1. Balinese Royalty - This theme is seen in Ep 02 - The Job of a High School Host! and Chapter 02 of the manga. The male hosts wear Balinese royal garb and Music Room #3 is transformed into a lush, tropical jungle with the temperature of the room reflecting the humidity and heat of such a place. Tamaki gets the idea from a travel brochure on Bali given to him by Kyoya.
1a. The Dance Party - While not a theme, per se, the hosts appear in dressy outfits, including Haruhi who is later made to dress up like a girl (!) The Dance Party occurs at the end of The Job of a High School Host!
2. Garden Tea Party - This theme is seen in Ep 03 - Beware the Physical Exam! and Chapter 04 of the manga. Tamaki, Kyoya and the twins appear as cafe waiters while Mori, Honey and Haruhi wear yukatas. The host club conducts their event in an outdoor garden.
3. Japanese Traditional - This theme is seen in Ep 04 - Attack of the Lady Manager! and Chapter 03 of the manga. The hosts are all dressed in kimonos designed by the twins' fashion-designer mother, Yazuha Hitachiin. The Music Room is adorned with traditional Japanese decorations.
4. An Arabian Palace - This theme is seen in Ep 06 - The Grade School Host is the Naughty Type! and Chapter 06 of the manga. The music room is turned into an Arabian palace with Tamaki dressed as an Arabian sheik while the rest of the hosts dress as Arabian traders and warriors.
5. Brave Knights - This theme is shown in Ep 09 - A Challenge from Lobelia Girls' Academy! The male hosts wear colorful armor and musketeer ensembles, but the room remains plain.
5a. The Sweetie Campaign - This secondary theme is also seen in A Challenge from Lobelia Girls' Academy! Except for Mori who wears the garb of a cavalier, all of the other male hosts are decked out in ball gowns and full makeup. In the manga, the twins and Honey are the only ones dressed as girls. Tamaki devises this as a way to convince Haruhi to stay at Ouran Academy.
6. Law Enforcement - This theme is seen in Ep 11 - Big Brother is a Prince!. The hosts all wear uniforms from various police groups and ranks. Mori, Honey and Kyoya are seen in their police outfits once more in a scene from Ep 16 - Operation Haruhi and Hikaru's First Date!, when they seem to be in an interrogation room, cross-examining Haruhi.
7. The Heian Era - This theme is shown in Ep 14 - Covering the Famous Host Club! The hosts are dressed in ensembles from the Heian era of Japanese history. The event is held, once again, in an outdoor garden made to look as it might have appeared during the Heian era.
8. Halloween Vampires - This theme is seen in Ep 21 - Until the Day it Becomes Pumpkin! The male hosts are dressed as elegant vampires and the music room features Halloween decor.9. The Edo Era - This theme is seen in Ep 22 - Mori-senpai Has an Apprentice Candidate! The music room is decorated to look like the Ikedaya Inn, which is a famous place in samurai history. The hosts all wear matching samurai garb and forehead protectors, with Tamaki dressed as the leading shinsengumi warrior.
10. The Ouran Fair - This theme is seen in Ep 25 - The Host Club Declares Dissolution! The hosts wear two different formal outfits - the first being matching serving outfits with vests and bowties, the second being matching tuxedos with tailcoats. The event takes place in the Central Salon of Ouran Academy which is open to the general public during the fair.11. 18th-Century French Nobility - This theme is seen in Ep 26 - This is Our Ouran Fair! All of the hosts except Tamaki appear as 18th century French nobility for the final day of the Ouran Fair. Haruhi's costume has her dressed as a girl.