Ultra Sonic is a memorable episode as it had a few pivotal moments. We have the first in show appearance of Uncle Chuck and understand the problem of robotication. Sonic also comes close to crying in the end when he has to leave Chuck behind. The crying apparantly pissed Sega off, who forbade DIC to show such emotion for Sonic again. Kinda hypocritical, when you think of all the crying in eps. 77/78 of Sonic X.
Despite the moments, this episode wasn't of the best quality. Uncle Chuck acts a bit like a monster/zombie before they give him his free will. Sonic takes on a few SWATbots but the fighting is stop-start. And the crystal's removal destroying the ecosystem was a bit unexplained.
This episode is worth seeing, but mainly for its moments.