When it was a telemarketer, we'd say "just a moment" and then sit the phone in front of the TV speaker. You'd hear little buzzy "hello? hello?" punctuating Jerry and George's coffee shop banter. It was funny. Other times my friends would make sex noises in the background. Also funny.

Another fun one was answering the phone with a question like "is Becky there?" This would always throw them off. Can't do any of this nowadays because now they just note that your number is an active one and sell it to data brokers (which is why I will never have "read receipts" activated on my phone)