Ack-Ack Macaque

The author of a cult anime series about a macaque who serves in the British Air Force in WWI sends her boyfriend into a deep depression when she leaves him for a marketing executive, who develops the character into a huge global commercial success; when she realizes how the character has been diluted for the mass market she leaves him and returns to her former boyfriend, but the character, now powered by the vast computing resources of the marketing company, breaks out of the simulation and wreaks havoc when it takes its military mission to the whole Internet.