Goku in the Anime Didn't Need to Rely on Gohan For the Cell Games Fans have debated whether or not Goku could mix Super Saiyan with Kaio-Ken for as long as both forms have existed. It’s not hard ...

Beast Gohan is admittedly a bit difficult in this regard because it's a "singular talent," to quote Whis. No one knows about it or expects it to happen, so its appearance is something of a surprise.