Eugene the Jeep was inside the box, and he was not a dog at all.
In the 1936 strip headlined "Wha's a Jeep?" Professor Brainstine explained that the Jeep is an animal belonging to a fourth dimensional world.
A few Jeep life cells somehow forced its way into our three dimensional world and at a favorable time they combined with free life cells of the African Hooey Hound.
The result was a yellow creature, the size of a dog with a bear-like head and ears but with a large nose. It has a long tail and a protruding belly and walked on its hind legs.
The most amazing thing about Popeye's strange pet is that he can disappear from one place and reappear in another using a limited form of teleportation. Eugene can also walk through walls. The Jeep is unable to tell a lie and can help humans to solve complex problems.
It is said that World War II soldiers were so impressed by the Willys MB that they named it Jeep! They said it was small, able to solve seemingly impossible problems and appeared to be able to move between dimensions – just like Eugene the Jeep!
