I remember watching an episode of The Mummy: The Animated Series on Cartoon Network. Here are the details I remember:
Imhotep gave Einstein a task to solve the mystery of a map.
Einstein fooled Imhotep by solving equations on the blackboard and, in the end, giving him the wrong coordinates.
At the very end, Einstein told Alex that he made a fool of the mummy. Upon being asked where the real coordinates were, he pointed to his own brain and said, "here".
"The Black Forest", the seventh episode of season 1. According to a plot summary on TV.com (emphasis mine):
Imhotep has the book, but Evy knows the only man alive that is brilliant enough to understand it. That man just happens to be her old Professor, a man named Einstein. Colin and Imhotep, knowing the same thing, kidnap Einstein before the O'Connells have a chance to arrive in Einstein's hometown of Berlin. The Manacle gives Alex a vision of standing before a castle, then being inside it while the Mummy enters, and then of Einstein working on a blackboard. He quickly draws the castle in his notebook, and tells his parents that he thinks he knows where Einstein's being held. It's in the black forest, which was enchanted by the Mummy. The trees, more or less alive now, grab Jonathan, Evy, and Rick, sending them to an underground dungeon in the castle. Alex doesn't get caught, and goes off looking for the Castle, which he finds after a struggle or two. Jonathan, Rick, and Evy are tied up, but Rick tricks Colin into helping them escape. Alex frees Einstein, and as they walk down the hall, Alex tells the professor that his mom had studied with him. The professor remembers a young Evelyn Conaghan, very fondly. Einstein, now free and with the team outside the castle, tells Evy he's got the formula. Colin and Imhotep think they have the answer, as Einstein had left an answer on the blackboard. They don't know that the answer is just the opposite of the real one! Einstein has been a teacher long enough to know that he should never put the real answers where anyone can read them! Einstein gives them the coordinates and they're off!
I can't verify the last point, but this is the only episode I can find that features Albert Einstein.
