When wearing the costume, "E=MC2" appears in a thought bubble when spacebar is pressed.
Einstein is a pack in the Poptropica Store which you can buy for 75 credits . It includes two items - a book called Who Was Albert Einstein? and a costume to customize so you could look like Albert Einstein. It came out to commemorate the 57th anniversary of Albert Einstein's Birthday. When you press the space bar, his world-famous equation, E=mc2 comes out in a thought bubble. You can read a chapter of the book.