Answering Machine - Subtle Changes

This is John. I can't come to the phone right now, but if you leave a message at the tone, I'll return your call. (Now, re-record the message every morning. Frequent callers will notice that something sounds different, but will be confused since the words are exactly the same.)

Answering Machine - Joe Friday

In Joe Friday voice: This is Constable Augie of the Canadian Security and Intelligence Service. The phone line you have just dialed is currently under investigation on a warrant issued by the Attorney General of Canada. To facilitate our investigation, we would appreciate you leaving your name, number, a brief message, and any affiliations you may have made now, or in the past, with communist or terrorist organizations. Thank you. 

Bowling Alley Prank Call

Call a bowling alley, and ask, "Do you have 10 lb. balls?"
When the attendant says yes, ask, "Then how the hell do you walk?"