Mug cakes in the oven? I'm planning a party and want to make multiple mug cakes, but since I need to make about 100 and don't have a microwave that big I was wondering if I could make them in the oven and if there were oven safe mugs. I've been looking but they all seem to say dishwasher and microwave safe but nothing about the oven. Would it be easier to make them in the microwave one at a time? Just seems like a hassle.
A microwave has a very different mechanism of heating than an oven, and recipes for the two are not interchangeable. The results of making microwave-optimized cakes in the oven will be unpredictable. And this will be a much larger problem than having the right mugs. 

A better option would be to find a recipe for muffins or cupcakes that is intended to go in the oven, and bake it in the oven. Do test it in a small batch before giving it to 100+ guests, because not all recipes floating around are good - but still, it is more likely to produce good results than baking your microwave cakes in an oven.