Here is a story I copied and pasted, like a true mouse potato, from here.
It all started with a couch, a bag of potato chips, and an endless supply of television. The couch potato phenomenon has now spread into the computer gaming and Internet communities, creating a new sedentary human tuber known as a mouse potato. A mouse potato spends an excessive amount of time in front of a computer monitor, often exhibiting the same lack of interest in the outside world as the original television-addicted couch potato.
The term "mouse potato" is believed to have entered the popular vernacular in 1993, although the phenomenon itself was not completely unknown until that time. Some early computer enthusiasts, particularly gamers, were already spending numerous hours a day in front of their monochrome monitors, only leaving their keyboards long enough to eat or sleep.
Because a number of modern computer games are designed to engage the user for a seemingly endless amount of time, some users find themselves so addicted to game play that the idea of leaving the computer seems counter-productive. Others find themselves performing extensive Internet searches or participating in online chat rooms or attempting to keep up with email and other computer-based correspondence. This is all in addition to maintaining one's own Internet presence through personal blogs, home pages and social networking websites.
With all of these enticing and time-consuming features of the Internet and computer world, it shouldn't be surprising that the number of mouse potatoes has grown exponentially in recent years. Even elementary school children as young as 5 have been known to exhibit early signs of Internet addiction and many will go through actual withdrawal symptoms whenever computer privileges have been revoked.
The mouse potato phenomenon has become a medical concern as well, since a sedentary lifestyle can lead to obesity, which in turn can lead to any number of diseases and health conditions such as diabetes and heart disease. Chronic mouse potatoes often fail to get enough restorative sleep between computer sessions, and may also maintain an unhealthy diet of convenience foods and excessive amounts of caffeine and other stimulants.
Some computer enthusiasts may spend several hours a day in front of a monitor but not be considered mouse potatoes by others. A true mouse potato often modifies his or her personal lifestyle to accommodate his or her computer habits, not the other way around.