I call him "Petey". In fact, the fact that Steamboat Willie's copyright expired in the US has led me to write a short story where Mickey Mouse has a gender transition into Minnie Mouse!
https://docs.google.com/document/d/1VGDgWFLfhqBh0BJCUXDJ7eZCXyAxdfbN-D1opJsk6iY/...