In the legendary rivalry between Microsoft and Apple, there have been many subjects of dispute. But this may be a first. And no, the headline above is not from The Onion.

Microsoft, opposing Apple’s attempt to trademark the phrase “App Store,” today filed a motion with the U.S. Patent and Trademark Office to strike the iPhone maker’s latest filing in the case — saying that its response to Microsoft’s attempt to dismiss the case violated court rules that limit such briefs to 25 pages, and require them to be in at least 11 point font.

“Apple’s response brief is 31 pages, including the table of contents and table of authorities, and on information and belief, is printed in less than 11 point font,” reads the motion filed today by Microsoft’s lawyers, accusing Apple of manipulating the text to squeeze in more of its arguments against Microsoft’s opposition to the trademark application.

The company asks the trademark court to require Apple to file a new brief that “complies with the rules and does not add any new matter or arguments.”

Here is the Microsoft motion: PDF. And here is the Apple motion Microsoft is trying to strike: PDF