Something hit me when I was re-watching the episodes, and I thought of a nice theory that can explain why Educational Egg appears to be good sometimes and why he appears evil for other times. Feel free to add more if you can think of any. I might add more in the future.
A Split Personality Caused by a Relationship with His Previous Girlfriend, Mary
What's crazy about Educational Egg is that he can seem evil at one moment, but good at another moment. Take episode 3 for example. At the beginning, he had a completely different voice and a very odd look on his face. He was asking "Mary" not to leave him and telling her that she's all he has left. (Possibly a reference to the ending of episode 2, when he said that his blood is cold because he chews ice out of sexual frustration, and Mary leaving him may be the reason that he suffers from sexual frustration.) Seconds later, though, he is calling Danny, which most likely shows that his good side is trying to escape from the grasp of his evil side.
Whether he's just recalling a conversation with Mary (most likely before episode 2, and maybe even before episode 1) or just confusing Danny for the hell of it, he turns into a completely normal person and stays that way throughout the remainder of the episode. He even attempts at being educational, especially when he explains to Danny that he accidentally drew Latvia instead of a circle, and when he attempted to guide him to the knowledge of what a real circle looks like. (And failing, of course.)
I think it's because of Mary that his evil side shows up. When he doesn't think of her and tries not to miss her, his good side shows up. He must have given up and let his evil side take over since episode 4. Speaking of episode 4, he also ate his son, probably one he had with Mary. He probably ate his son because his son reminded him of Mary too much.
If only Educational Egg explained all this to Danny, who's confused enough as it is.