Sentinel One, the supercomputer who works with the Space Sentinels from the Space Sentinels show.
I first saw this show when I was 5-6 years old. Sentinel One freaked me the hell out the first couple of times I saw it. It was a floating head that would just pop up! I got nightmares from that bit of cartoon. Well, that and a commercial that had the Universal Monsters with Joe Cocker's version of "You Are So Beautiful". When Karloff as Frankenstein showed up, I screamed my head off.
I was a weird kid.