It may seem like a problem that Goku has obtained Super Saiyan 4 before Dragon Ball Super, but there's actually a convenient ...

The anime often strays from Akira Toriyama's vision, so if you're an anime-only, you might have missed some crucial details ...

Many different kinds of fusion between the Saiyans have been shown, but there has never been one between 2 Super Saiyan 3's!