ThinkPad G series
This category is not about the Lenovo G series, which is part of the Lenovo 3000 Value Line.
The G series was developed as a very configurable budget machine in mind, allowing for a wide variety of configurations that could be either slow and cheap, or fast and expensive. To achieve this, the G series used the desktop Pentium 4 line, as they were mostly much cheaper than their mobile Pentium 4 equivalents. However, the disadvantage of the desktop Pentium 4 line had to be accounted for in its design. Which, resulted in a machine that was very thick and heavy.
In its later days, the G series used mobile processors. This started with the G41, and ended with the G50. As there was no other reason to continue with the G series, due to the competition from the thinner laptops, it eventually concluded with the G50.