Mister Rogers Heat Changing Coffee Mug - Add Hot Liquid and Watch Mr. Roger's Sweater Change Color - Comes in a Fun Gift Box - by The Unemployed Philosophers Guild The Mister Rogers mug features several quotes from the beloved television host, and when you add a hot beverage, Mister Rogers changes into a comfy sweater. 14 oz. mug. Heat changing mugs are microwave safe, but not dishwasher safe. From the Unemployed Philosophers Guild. Don't worry. We are employed, just not as philosophers. We're a small, Brooklyn based company specializing in gifts for the sophisticated gift giver. For whatever you need, we have presents of mind.