Twin Signal (ツインシグナル — Tsuin Sigunaru) is a manga series written by Sachi Oshimizu that ran in Square Enix's Monthly Shonen GanGan and later Monthly GFantasy from December 1992 to December 2001.
Dr. Otoi, the world's most eminent robot scientist, has just finished work on Signal, his most incredible creation yet. Made from MIRA, an almost supernaturally strong substance with regenerative properties, Signal will be both incredibly strong and incredibly lifelike. As a gift to his grandson, Nobu, Dr. Otoi asks him what sort of personality to give his new robot. Without hesitation, Nobu answers: "Like a big brother!" Which would all go quite well if Nobu didn't sneeze during the programming.
Now Signal is the pinnacle of combat robot technology, with a huge glitch: Every time Nobu sneezes, he transforms in a hyperactive Fun Sized "Chibi Signal" with an adoration for chocolate. In some ways, though, it's preferable to the full-sized Signal, who is what is technically known as an "arrogant airhead". He's in good company, though, as his family includes the Brilliant, but Lazy (beautiful) robot scientist Chris, Dr. Otoi's notoriously spacey son, and a host of adorable but inexplicable mini-robot creations.
Of course, with great technology comes those who want to steal said technology, and Dr. Otoi's old rival and colleage, Umenokoji, is after the MIRA Signal's made up of. He plans to kidnap Signal by first kidnapping Pulse, Signal's older brother/prototype, who would technically be inferior if his creator, Dr. Otoi's son, hadn't just decided to randomly upgrade Pulse with some new super-weaponry. Thus kicks off a series of wacky hijinks involving robot battles, super-science, robot battles, unlucky policemen, robot battles, kidnapping plots, robot battles, and did we forget anything? Oh yeah. Robot battles.
- Absentminded Professor: Seems to run in the Otoi family.
- Aloof Big Brother: Pulse, though that's not exactly his fault.
- Bait-and-Switch Credits: Absolutely nothing in the opening actually happens in the show. The events and characters do appear in the manga, though only one volume was ever officially translated into English.
- Battle Amongst the Flames
- Big Brother Bully: Dr. Otoi worries that Signal will develop this personality when Nobu suggests making him a big brother type. He does, in part, though he still cares deeply for Nobu.
- Blind Without 'Em: Pulse should really get some glasses.
- Brilliant, but Lazy: Chris is a very smart robotic engineer, usually, she just lacks drive.
- Copy Protection: In-universe, the MIRA file data is protected by... a whack-a-mole game featuring Chibi-Signal. It Makes Just As Much Sense In Context.
- Curtains Match the Window: Chris has pinkish-red hair and eyes, Nobu's hair and eyes are the same shade of brown, and an argument can be made for Signal, though his aquamarine hair just slightly mismatches his eyes.
- Dancing Theme: The ending theme, with cute dancing robots.
- The Ditz: Erala doesn't exactly have the most expansive CPU.
- 11th-Hour Superpower
- Fanservice: Signal is a walking fountain of fanservice.
- Flawed Prototype: Pulse is incredibly powerful... but needs to rest often due to his huge energy expendature. He's also very nearsighted.
- Fun Size: Chibi-Signal.
- Head Pet: Nobu has a mostly-unexplained foxlike friend who lives on his head, and who occasionally causes him to sneeze.
- Hot-Blooded: Signal, to the point where he's frustrated by living in such a peaceful town.
- Hypocritical Humor: "It's wrong and dishonorable to take advantage of someone when he's weakened! Now let's knock out Pulse while he sleeps!"
- Involuntary Shapeshifter: Nobu's sneeze triggers Signal's transformation from regular size to chibi-size and back again.
- Jerk with a Heart of Gold: Big Signal acts like a pretty normal big brother, which means he bounces between knocking on Nobu and being nice to him.
- Keet: Chibi-Signal.
- KidAnova: Nobu tries, anyway, especially where Erala is concerned. Chris makes fun of him for going through puberty.
- Leitmotif: Epsilon has a hilariously inappropriate leitmotif. It sounds like cutesy elevator music. Epsilon himself isn't really the elevator music type.
- Lethal Chef: Erala. Her habit of breaking every dish probably contributes to this.
- Little Big Brother: The younger of the two henchmen brothers is gigantic; the older is teeny-tiny.
- Long-Haired Pretty Boy: Both Signal and Pulse have long flowing locks.
- The Mind Is a Plaything of the Body: Big Signal has the typical arrogant big-brother personality, but Chibi-Signal is friendly and cutsey, if obsessed with chocolate.
- Mobile Shrubbery: Umenokoji's henchmen attempt to sneak out with the help of some obliging bushes.
- Nice Job Breaking It, Hero: Pulse wouldn't be such a threat if the younger Dr. Otoi hadn't chosen that exact moment to upgrade Pulse's weaponry.
- Next Sunday A.D.: There's a ton of advanced robotics running around, but the world still looks mostly the same.
- Nothing Exciting Ever Happens Here: Both Signal and the one policeman are driven bonkers by the fact that they live in such a peaceful town.
- Pigeonholed Voice Actor: In the Japanese dub: Signal is the most bishie robot ever, so let's get the most bishie-voiced actor to play him!
- Pity the Kidnapper: Erala is so ditzy and clumsy, she is probably not the world's best hostage. Even once she realizes she's been kidnapped, she's too concerned with cleaning for her life to attempt a serious escape.
- Power Dyes Your Hair: Signal, in his super-form, becomes white haired - this would probably be a spoiler if it wasn't in the opening.
- Ridiculously Human Robot: Robots still have metallic-looking limbs, but for the most part, many of them look identical to people. MIRA is even especially stated to make Signal extra-lifelike.
- Robo Family: Signal considers both Pulse and Nobu his brothers. "I was made to act like Nobu's brother. But I am his brother."
- Sharpened to a Single Molecule: Pulse's Blades Below the Shoulder are defined as "monomolecular".
- Trademark Favorite Food: Chibi-Signal loves chocolate.
- Transformation Sequence: Chibi-Signal-to-Big-Signal has a very dramatic one, complete with Clothing Damage. The first time he does it on screen, the wind of power destroys a library.