Knock Knock - Remember

Bob: "Will you remember me tomorrow?" 
Bill: "Yes"
Bob "Will you remember me next week?" 
Bill  "Yes"
Bob: "Will you remember me next month??"
Bill: "Yes"
Bob: "Will you remember me next year?"
Bill: "Yeah"
Bob: "Knock Knock"
Bill: "Who's There?"
Bob: "See, you forgot me already!"

Spray Down

Q: Why do black people have white hands and feet?
A: That is where God stood them up against the wall to spray them.

Knock Knock - Cow

Knock knock.
Who's there?
Cow goes.
Cow goes who?
No, cow goes "Moo!"