When someone prank calls you, what do you say to make their call backfire?

Okay me and my friend are just sitting here looking at stuff on freestuff.com right? when someone calls my cell with a RESTRICTED number and they said they were from a mustard company, and my friend said something back but we need a better backfire plan then ''Spencers Sperm Bank'' and ''Marty's Mortuary'' ..........HELP US!!!!!!!!!!!!