April 09, 2003
During a cutscene in the game, Jen smashes a tombstone which reads "R.I.P. Laura Cruft 2003", a reference to the main character of the Tomb Raider franchise, Lara Croft.
Primal was made by SCE Cambridge Studio and published by Sony Computer Entertainment, while Tomb Raider games were still developed by Core Design and published by Eidos back then. Despite that, the reference is minor and thus not really a copyright infringement.