So, Rockruff is what hold /vp/ actually in hype and it seems to be a big deal.

But, I think that's nothing special, nothing so important, let's do some analysis:

- The "secret" is being teased only once in Corocoro (And only there) so this makes me think that's not big of a deal

- It can't be "own special Z moves" since Snorlax have one and this secret is releated only and only to Rockruff and starters

- It can't be the split evolutions: this seems very unlikely beacuse the Pokèdex shows up only 3 slot for every starter (1st stage, 2nd stage and 3rd stage)

- It can't be Type:Null chimera experiment, like lot of people like Me said, Type:Null has various parts in his body but definitevely not parts of an Owl or a Sea Lion, it can fit the feline part of Litten but it got violet "things" on that part so we can exclude litten aswell

- It CAN BE synchro forms, yeah, synchro forms, maybe special Z stones that turns our pokèmon in a synchro form when the battle starts (Like Ash do in the anime), and it can be very good theory beacuse they said the starters this time are going to be an important piece in the story
Here I think they want to enchant the starter - trainer bond

TL;DR: Even I was teased and hyped for the Day and Night evolutions but that will not happen, it will be just a synchro form when the battle starts if nothing lower than that