Let Me Tell You Something wrote:Spitter is probably going to appear in the next Ben10K sequence, leaving Fasttrack and Jetray without hints at appearances. The excuse for Jetray is that he has appeared too much beforehand and Fasttrack's is probably that most people hate him, but they should just give the 4 remaining aliens some appearances so they can just say they had all in one series.
Chromastone and Swampfire had basically no screentime, too, though I suspect for Swampfire it's because the voice hurts Baker's throat.
Derrick said that Spitter hadn't been used, that's all. No hint at future Ben 10K uses or anything, and Ben 10K doesn't work like that anyways. There's no real excuse for any of them, really. Like Painlee said, aliens like Humungousaur were used far more than Jet Ray, but they've made returns. They just haven't used those aliens. It's puzzling and not pleasant, but it is what it is.
Also, it wasn't Swampfire's voice that hurt Dee's voice, it was Humungousaur's. Which is probably part of the reason why DiMaggio voices him now....