When Goku turned into SSJ3 against Janemba.

[Let's Go Fearless!]

Spoiler

What is that blue stuff anyway?

 

[Future Warrior]

His dormant Super Saiyan Blue power

 

[SSJ2]

The dimension was warping.

 

[Pyro]

Yes, it's the dimension warping around him. Quite spectacular for a mere Super Saiyan 3.

 

[Future Warrior]

Well, Super Saiyan 3 wasn't really a force to be trifled with at that time.