Try putting that in a Christmas cracker??
‘There were two men,’ Bill Morrison said as they dug into the Stilton. It took Teddy a moment to realize that this was the rather ponderous introduction to some sort of witticism. ‘One of them was from Yorkshire, God’s own country. The other one wasn’t a Yorkshireman. The one not from Yorkshire said to the other (Teddy began to lose track at this point), “I met a Yorkshireman t’other day,” and the one from Yorkshire said, “How’d’ tha know he were from Yorkshire?” And the one not from Yorkshire (now Teddy began to lose the will to live) said, “Because of his accent,” and the Yorkshireman said, “Nah, lad, if he’d been from Yorkshire it would have been the first thing he would have told you.”’
‘Try putting that in a Christmas cracker,’ Nancy said when Teddy attempted to relate it to her that evening after rolling home, somewhat foxed.
I would like to know what does "Try putting that in a Christmas cracker" here mean. Thanks.