Final Doom, which I posted a while ago, isn't the only game that supports both - the PlayStation Serial Link Mode as well as the PlayStation Mouse! So too does Command & Conquer Red Alert!
This lead me to one of my favourite pics I've taken of my #retrogaming shenanigans!
My two TV, two PS1s, linked by serial cable - the TVs are both showing different areas of the RTS map
My two TV, two PS1s, linked by serial cable - the TVs are both displaying the Command and Conquer Red Alert title screen
My two TV, two PS1s, linked by serial cable - the TVs are both displaying the big Hammer and Sickle logo of the Soviet Disk being loaded on both systems