PSP classic Super Stardust Portable has been quietly added to Sony’s PlayStation Plus Premium games list, though is currently a little difficult to find.
The handheld shoot ’em-up, originally launched in 2008, can be found by searching directly for the title in the PlayStation Store (thanks to reddit user Turb0_Thunder).
You won’t find it (yet) via the Classic Catalogue menu, although it’s unclear if this is because it’s not due to go live yet, or a deliberate secret. (Either way, PlayStation’s store interface isn’t the clearest to filter and search through.)