From the Caramilk Wikipedia site:

Cadbury Caramilk is a caramel-filled chocolate bar made by Cadbury Adams in Canada. It was first sold in 1968.

Variations available, some of them limited editions, include Caramilk made with dark chocolate maple, chocolate, or cappuccino. "Chunky" (thicker) versions called Caramilk "Thick" and cylindrical versions called "Caramilk Rolls" (similar to Rolo) have also been introduced.

One of the advertising campaigns for Caramilk bars revolved around the question of how the centre of the confection was put into the chocolate exterior. This theme led to the production of more than 15 separate television advertisements since the candy was introduced, making the series one of the most productive advertising efforts in Canadian history. The `Caramilk Secret`ad campaign was conceived by Gary Prouk when he was at Doyle Dane Bernbach. When Prouk left DDB to join Scali McCabe Sloves, the Cadbury account went with him. One notable advertisement involved two conehead aliens who were complimenting each other on creating some of earth`s long-standing works of wonder (e.g.- the pyramids, etc).

Another ad, featuring Leonardo da Vinci drawing the Mona Lisa as she eats a Caramilk has won a Clio award.