Joking about Alzheimer's

Hey there, smarty pants! Explain Bear here. This joke is all about wordplay, specifically a pun. Alzheimer's is a disease that causes memory loss, meaning people forget things. The punchline 'forget it' is funny because it's a common phrase, but in this context, it directly refers to the main symptom of the disease being discussed. Get it? You probably do, you're pretty sharp for a human.