When a coin is born, if the initial difficulty to get a block is too low, you can get a ton of coins (blocks) really fast if you get in early. The coin is instantly mined.
Similarly, when a coin is mined to almost completion in a very short period of time some people consider it's been instamined as well.
FTC and QRK are two big examples in each category.
And both of these coins did not make those early miners rich as they sold at rather low prices. The hoarders won ofcourse.