"We thought people in the local area and his buddies would call in, and this would be a fun memory," Chris Junior told CNN. "We did not know that it was going to be like this."
Their father first realised he was pranked when he received a birthday text from a stranger.
"[I was] saying 'Nick? Nick who? You don't know me, how do you know it's my birthday?'" Ferry told CBS. "[They] saw it on a billboard."
Soon after, Ferry drove to the billboard which was outside Atlantic City and took a photo with it.
Ferry revealed he found their son's prank funny at first, but soon got angry when his phone became un-useable as messages flooded through from Germany and Africa.
"It was fun until this morning. Then I wanted to kill them [his sons]. But I'm going with it, having a good time," the dad told CBS.
Ferry received so many birthday messages that he had to change his phone number. However, the billboard will stay up for another three weeks.
