Debuting in 1943, the Batcave is a fascinating place that holds many mementos to Batman’s long history. The Caped Crusader's lair features many interesting items such a giant penny and a large replica of Joker's playing card. Though some may say it's ridiculous, the cave is a reflection of Batman's character evolution. Despite going through many changes over the years and different iterations across creative teams, one of the few items that remains constant is the iconic T-Rex prop. The origins for this unusual memento go way back into Batman's formative years.
The basic origin story for the T-Rex has remained fairly consistent over the years, having first debuted in a story in Batman #35 by Bill Finger and Paul Cooper. In this issue, Batman and Robin are asked to attend a charity event at Dinosaur Island, a prehistoric theme park. This turns out to be a trap, and the two are attacked by mechanical dinosaurs controlled by a criminal named Stephen Chase. The dynamic duo defeat the criminal, and following their victory, they simply take the T-Rex home as a trophy.
However, the post-Crisis origin features a modernized take on the aforementioned story. In Batman Chronicles issue #8, by Graham Nolan, we learn that Murray Hart, an old friend of Bruce Wayne has been murdered. The coroner rules the death a suicide, however, Bruce has his suspicions. Prior to her death, Hart had been running Dinosaur Island with her partner Stephan Chase, which was intended to be an informational amusement park. Chase had a different idea, wanting to turn the park into a horror-themed attraction. This key difference is what Batman suspects led to Chase killing Hart.
Batman travels to Dinosaur Island to find Chase and is met with an attack from animatronic dinosaurs. One of these happens to be a T-Rex, which is being controlled by Chase. Batman is able to apprehend him, however, upon returning to the Batcave, he is met with a feeling of hopelessness. He questions his efforts throughout his time as Batman, wondering if he is really making a difference in the grand scheme of things. Alfred suggests that Bruce needs help putting things into perspective and has an idea of his own. To help Bruce remember his accomplishments as Batman, he goes to a police auction and is able to obtain the animatronic T-Rex, keeping it as a reminder of all the good that Batman has done for the people of Gotham.
The T-Rex is not solely a trophy, however. The animatronic (Nicknamed Fido) has been used by Batman as a security measure against intruders in the Batcave, having been utilized to fend off attacks from Hush, as well as the Court of Owls. The dinosaur has also appeared in other forms of media, having been seen in Batman: The Animated Series, the Arkham video games, and The Lego Batman Movie.
The Batcave serves a significant purpose in the Batman mythos, and as a result, it is fitting that it is full of monuments to over 80 years of Batman's history. As the character continues to progress, it will be interesting to see what new monuments appear in the cave. One thing that is for certain though, is that Fido will remain a fixture in the cave for years to come.