Koitsu, Aitsu, Soitsu and Doitsu

Koitsu (こいつ^?), Aitsu (あいつ^?), Soitsu (そいつ^?) and Doitsu (どいつ^?) are recurring playable characters in the Parodius series. They resemble little stick men flying on paper airplanes.

Background

Their names are commonly used in Japanese slang terms to refer to people one doesn't know:

Koitsu = this guy
Aitsu = that guy (far from both chatters)
Soitsu = that guy (far from the speaker but near to the listener)
Doitsu = who?

Weapon set

Gokujō Parodius!

S: Speed Up
M: Homing Missile
D: Round Shot
L: Wave
O: Grade Up
?: Aura

Sexy Parodius

S: Speed Up
M: Strong Missile
D: Round Shot
L: Wave
O: Grade Up
?: Aura

Other appearances

Yu-Gi-Oh! - They appear as playable monsters in this trading card game. Their full power cannot be utilized unless they're played in pairs.
Castlevania: Portrait of Ruin - Cameo as a sub-weapon skill.
Castlevania: Harmony of Despair - Cameo as a sub-weapon skill.
Kuru Kuru Lab - Koitsu appears as a character.
Speed King - Aitsu is a playable character.

Gallery

Gokujō Parodius! ~Kako no Eikō o Motomete~
Characters	Takosuke and Belial • Vic Viper and Lord British • Pentaro and Hanako • TwinBee and WinBee • Hikaru and Akane • Mambo and Samba • Michael and Gabriel • Koitsu and Aitsu • Goemon and Ebisumaru • Dracula-kun and Kid Dracula • Upa and Rupa • Mr. Past Glory
Stages	Circo Porto Harborland • Cat Battleship Forever • Candy Land • Traffic Signs • Core Ship Parade • Moai Battleship • The Moon • Disco • Shooting Memories
Bosses	Anna Pavlova • Cat Submarine • Eliza • Decoration Core • Crazy Core • Capsule Monster Cappuccino • Yoshiko • Princess Kaguya • Chichibinta Rika • Tako's Cutie • Pentaro X

Jikkyō Oshaberi Parodius
Characters	Takohiko and Belial • Vic Viper and Lord British • Pentaro and Hanako • TwinBee and WinBee • Sue and Memim • Mike and Ran • Soitsu and Doitsu • Upa and Rupa • Dracula-kun and Kid Dracula • Mr. Past Glory
Stages	Hip Hop Disco • School • Donburi Fields • Edo • Sweet Land • High Speed Patrol • Fiesta Base • Polygon Space (Omake 1) • Grand Prix (Omake 2)
Bosses	Mirror Ball • Judy • Enormous Hikaru and Akane • Mardock and Warumon's Ships • BaronBee • BoinBee • Goemon Compact • Decoration Core MK II • Cat Battle Train • Big Core MK I (SNES) • Ghost Woman (SNES) • Big BaronBee (SNES) • John Wanjiro (PSX) • Penkuro (PSX) • Temple Lord • Mr. Goldfish's Selling Fortress • Chichibinta Rika • Bacteriya • Robot Wall

Sexy Parodius
Characters	Vic Viper and Lord British • Ivan and Toby • Hikaru and Akane • Mambo and Samba • Michael and Gabriel • Koitsu and Aitsu • Option and Multiple • Shooting Star and Black Viper (Ace) • The Old Lecher Tako
Stages	Farm • Bath House • Underwater Palace • Castle Dracula • Girl Factory • Coal Mine • Sweet Sky • Boss Rush • Taj Mahal • Special Stage
Bosses	Corn Chiwa • Finally Penguin • Otohime • Medusa • Transporting Crane • Tanuko the Tanuki • Candy Core • Capsule Monster Cappuccino • Captain Penguinovski the 3rd • Eagle Eagle Sabnosuke • Hot Lips • Yuko • "Mon" • Kaori • Sexy Star