Legal Question in Intellectual Property in California

Well, first, to "pursue legal action" doesn't necessarily mean that the plaintiff has a winning case ......... lots of folks pursue legal actions and end up losing, because their case lacked merit, or they pursued it improperly, or they ran out of money, etc. etc. So, I can't assure you that you won't be sued and won't have to put up a defense. However, I would add that the term "Olympia" when not associated with a product (such as, for example, beer) is in the public domain. You are probably safe from suit unless your t-shirt design otherwise strongly suggests "Mr. Olympia," such as by copying their type style, or some other feature of Mr. Olympia's public image that causes others who see your t-shirts to associate them with the trademark and think they are looking at something made by or authorized by Mr. Olympia. In sum, slight differences from the actual trademark don't always protect you if your product comes so close to the trademarked item that the public readily forms an association and is confused into thinking they're seeing the trademark.