Pickle and Jack had known each other for a long time, thanks to Tokugawa who, even if it wasn't face to face, would explain to Jack about the prehistoric teenager. While Pickle didn't pay attention

Pickle was constantly used for experiments thanks to his characteristics that separated him from humans and the beings that came to inhabit his time. They had recently discovered that Pickle was nothing more than a 10-year-old pre-adolescent, who had developed that impenetrable skin, extremely sharp reflexes, like his eyes and hearing similar to those of a cat. That's why Tokugawa took Jack, because he was more or less the same age as the prehistoric pre-teenager

One day Jack, who kept seeing Pickle behind the glass, was incited by Tokugawa and the scientist who woke Pickle to go to the latter's place.

Pickle when he heard the door open, hid behind the tree that he had in that "room", thinking that it would be one of the scientists or military men who made his life impossible.