Thread:Blalafoon/@comment-11627944-20130805043841/@comment-768817-20130811011515

The rule is, to become Super Saiyan 1, you must experince extreme emotion the first time! Only once! Then you can do it on demand. The others you can do with out an extreme emotion trigger, as long as you have done it the FIRST time. Read the it, before you call it stupid.

And when Future Trunks turned Super Saiyan in Dragon Ball Z, they said that wasn't the first time he'd done it.