TCU’s in-state rivals are pretty easy to name: Baylor, SMU, Texas, etc. Once upon a time, though, TCU had a Metroplex rival in the University of Texas at Arlington, albeit a short-lived one.
UTA doesn't have a football team anymore — not since 1985. But when their football team did exist, they played the Frogs for a little more than a decade.
The Mavericks have since set their sights on basketball and baseball (not to mention its science and engineering programs).