Final answer:
Ian is nicknamed 'Mr. Pottery class' possibly due to his strong association with a pottery class; the nickname could reflect his skills or enthusiasm.
Step-by-step explanation:
Ian is called Mr. Pottery class by his peers or the narrator, possibly due to his association with or frequent participation in a pottery class. The context in which this nickname is used is important to understanding why he's referred to in this manner. For example, if the setting is within a school and Ian is known for his exceptional skills or enthusiasm in pottery class, it would make sense for others to refer to him by this nickname. However, without more context from the text or dialogue, it's difficult to provide a definitive reason as to who calls him this and why.