Quick Memory Loss

Son: Dad, will you remember me in 5 years? Dad: Yes. Son: 1 year? Dad: Yes. Son: 6 months? Dad: Yes. Son: 1 month? Dad: Yes Son 1 week? Dad: Yes. Son: 5 days? Dad: Yes. Son: 5 hours? Dad: Yes. Son: 1 hour? Dad: Yes. Son: 30 minutes? Dad: Yes. Son: 1 minute? Dad: Yes. Son: 1 second? Dad: Yes. Son: Knock Knock Dad: Who's there? Son: See, you forgot me already!!!