According to the Candy Professor, Chicken Dinner Candy Bars were introduced by the Sperry Candy Company of Milwaukee in 1923. They soon became one of the best selling candy bars of their day. Despite the name, they had nothing to do with chicken or dinner. The bar was a chocolate-covered nut roll. (Sounds pretty good!)
Wikipedia claims the name was a reference to President Herbert Hoover's promise of a "chicken in every pot." But that can't be right if the bars were introduced in 1923. The Candy Professor argues that the name was just an advertising gimmick to get people's attention.
Wikipedia also says that early TV commercials for Chicken Dinner Candy had a jingle that went, "Chick - Chick - Chick - Chick - Chicken Dinner" -- in the cadence of a rooster crowing.
The image of the Chicken Candy advertisement comes from an eBay auction. The seller wants $175 for the vintage cardboard advertisement, which seems a lot, though perhaps not if that's the kind of thing you collect.
Do you know why jokes and pranks like these don't fly any more? Because nobody gives a damn about playing their proper role these days. I'm not even going to mention the old lady with impossible neck and sadistic habits. But just look at that hobo! His hat has the classic open-can-lid top. He's wearing a Victoria Cross medal, cravat and vest. Note how carefully he cradles his cane on his arm. Note how delicately he takes the fake biscuit, with pinky finger upraised. The magnificent scowl when he bites the rubber biscuit! You'd consider your twelve cents well spent!
Now imagine giving a "surprise biscuit" to the modern incoherent and sloppily dressed drug addict sitting on the sidewalk outside your local liquor store. He'd be too out-of-it to even register the prank. If he did, he'd just grunt and toss the surprise biscuit one side, frustrating your enjoyment of your purchase.