The Skylanders' names (save for Spyro and Cynder) are nicknames.
Whirlwind is Rarity and Spike's daughter.
The Giants in the sequel are the Elder Elementals mentioned in the first gameThe first games mention Elder Elementals, powerful ancient Skylanders. The Giants so far revealed all have elemental appearences and are more powerful than the normal characters, so it would make sense.
Arbo is somehow related to Tree Rex.He says he has memories of the darkness threatening the Skylands before. And the last time that happened was when the first skylanders, the giants, first came together. Maybe Tree Rex unconciously sent a small part of his soul to that tree-flower thing in the ruins to subtly help the new skylanders with Kaos.
The Giants are related to other Skylanders of their element.More specifically the Giants are advanced species or mutations of other species
Skylanders will have more Activion characters than just SpyroSuch as Crash Bandicoot.
The reason Spyro looks so weird in Skylanders: Spyro's Adventure.....Toxic Waste. Yep. Skylanders Spyro is a mutant.
Gnasty Gnorc will be the Big Bad in a future game.
Kaos isn't an only child - the pictures in his castle in Giants are fake.Kaos resents his other siblings so he has fake portraits with them removed in his castle. This also can explain his mother's different appearance - being as egotistical as he is he probably had her pictured to look more like him