Garlic Jr first appeared in Movie 1: The Dead Zone. The story goes that his father, Garlic, was once in competition with Kame to be instated as the God of Earth. Garlic lost this small scrap and was a little annoyed. In his rage he attempted to overthrow Kame, he once again, lost. He was sent to the Dead Zone for his deeds.
Garlic Jr was still hanging around Earth and a few hundred years later in Movie 1: The Dead Zone Garlic Jr attempted to use the dragonballs to gain control of Earth. He was defeated by the youthful gohan in movie 1 and also when he returned in the mini-series in-between the Frieza saga and the Android saga.

Form 1

This is Garlic Jr's everyday form, although possessing great speed and agility he lacked the power he required in battle, that's the use for his second form.

Form 2

Garlic Jr's second and final form, this was seen twice, both in Movie 1 where he was overpowered by Chibi Gohan and again in the Garlic Jr saga where he was using the makioh star to boost his powers. Although being a reasonable villian he was overpowered both times by Gohan when gohan was at his weakest.