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The iDog is a robot dog toy designed and manufactured by Sega Toys, marketed by Hasbro in the United States. iDog receives input from an external music source, such as a MP3 player, lighting up and "dancing" to the rhythm of the music. It is also marketed as the eDog in Germany, Italy and the Netherlands.
Although the original iDog was designed by Sega, the iDog Amped, iDog Dance, iCat, iCy, iTurtle, and iDog Soft Speaker were all designed by Hasbro.
Basic iDog 
The iDog reacts to music from an external source, such as an MP3 player. It features seven flashing LED lights on its face and has the ability to 'dance' to the beat of the music. It also has a number of switches on its nose, head and tail which allow it to react to user input. It has various emotions (which change based on user interaction) that provide different color patterns on its LED lights. The iDog was designed to interact with the iPod, though it will work with any 3.5mm minijack audio connector input, and has an integrated speaker.
The iDog began shipping worldwide between March and April 2005. The iDog comes in several colors including white, black, pink, red, lime green, a tiger print, and a dalmatian print. Hasbro also sells decorative clothing for the iDog, called the "Chill" series, including feet-warmers, scarves, and ear-warmers.
iDog variations 
As a promotional tie in with Spider-Man 3, Sega manufactured iDogs resembling Spider-Man called the Spi-Dog. In 2007, Tiger Electronics released the iDog Amp'd, an upgraded version of the iDog with stereo speakers which nodded its head and tapped its foot in time to the music being played on it. The iDog Pup, a puppy version of the iDog with poseable ears and a moving head, was released in 2007.
In 2008, three new versions of the iDog were released. The iDog Clip is a fully functional mini-sized iDog which can be clipped onto a backpack. The iDog Dance is a larger version of the iDog that stands up and dances in time to the music. In 2009, Sega released the stuffed iDog Soft Speaker and the iDog plush puppy, which did not require batteries
Different kinds of music cause iDog to develop different personalities, as displayed through the color of LED lights that flash and blink on its face.
The iCat is a feline version of the iDog. Similar to the iDog, it reacts to music from an external source, such as an MP3 player. It features seven flashing LED lights on its face and has the ability to "dance" to the beat of the music. It also has switches on its tail, head (nose), and 6 touch sensors which allow it to react to user input. Like, the iDog, its LED light color patterns display various "emotions" based on user interaction and the music played.
A piscine version of the iDog, the iFish plays music and moves in a swimming-like motion. The iFish also has an internal selection of music. The iFish comes in white or black, with a 3.5 mm audio cable for audio input. Like the iDog, it is touch-sensitive.
The iCy is a penguin version of the iDog. In addition to playing music, it dances and the LED lights on its stomach flash in time to the music. Unlike its predecessors, it has only two touch sensors for user interaction: its tail, which is designed to annoy it rather than reward it, and its beak, which is used to pet it. It has various "emotions" which change based on user interaction and music played.
Hasbro sells decorative clothing for the iCy, called the "Chill" series, including hats, flipper-warmers, feet-warmers, and scarves.
The iTurtle is a turtle version of the iDog. It also comes with a plug cable (3.5 mm) with 2 touch sensors on its tail and head. It moves its shell up and down, shakes its head side to side, and taps its foot. Has the same things as others except his moods are modified.
Viral Marketing 
In 2006 in the popular podcast Daily Source Code host Adam Curry spoke a lot about the iDog and UK musician Jesta was inspired to write an entire song about it titled "Me, My Music & My iDog" which featured on the show and numerous other podcasts in the following weeks.
See also