Nazi Cola wrote:I don't think he went Super Saiyan 2. I think he was just powering up in Super Saiyan.
Toei pretty much just seems to show any SSjin 2 transformation but Goku and Kid Gohan's (they have distinct hair) as the user powering up/going Super Saiya-jin while already Super Saiya-jin. Going by Vegeta's aura, etc he likely went SSjin 2 against Super #17 the same way Goten did against Gohan.
Nazi Cola wrote:By that logic, does that also mean Vegetto was a Super Saiyan 2 for a split second upon transforming but then suddenly went right back down to Super Saiyan for no explicable reason (and with no visual change other than the lightning), because he had lightning initially?
I haven't watched the Bebi Goten/Gohan fight in a few months but I don't remember Gohan's hair changing or him being surrounded in lightning at all.

Goten passes out after Bebi attacks Gohan so while he only had lightning initially, he wasn't conscious enough for us to see if he'd continue to have lightning. Lightning doesn't mean someone is SSjin 2 but it's one of the only indicators for someone who isn't Son Goku or Kid Gohan; they're the only ones to have distinct hair in SSjin 2.
He had a storm of lightning around him and his shirt even got destroyed (SSjin 2s seem to be slightly bulkier than SSjins so it may be that.) About the hair, it's hard to tell and I admit I'm not 100% sure about this as we can barely see his hair in that scene but it SEEMS to me that it's changed somewhat.
Kaboom wrote:Officially, according to the GT Perfect Files, nobody in GT ever used Super Saiyan 2. Why? I dunno. It's GT. There's even a short bit in his battle with Rild where Goku's hair distinctly changes into its SSj2 shape...
But anyway, Toei has had a bad habit of throwing around the lighting sparks for special effect whenever they want, so that's not a sure-fire sign of SSj2 like in the manga.
Well as you yourself said, Goku goes SSjin 2 against Rild who that proves the GT Perfect Files wrong already. He also went SSjin 2 against Bebi the second time they fought. The first time he went straight to SSjin 3 but the first time he went through all of the forms.
SuperForteX wrote:It's not a sure-fire sign in the manga either. I can think of at least one SSj2 that lacks the sparks, and at least one SSj1 that has them.
That's definitely true. Even if you don't believe Gohan was a SSjin 2 against Dabra (I personally do,) there are other instances of users lacking sparks to look weak/weakened. Super Perfect Cell, Nappa, SSjin Vegetto, etc all have sparks too despite not being SSjin 2.