We don't really know why you would ever want to do this, but the backwards-compatible PlayStation 4 games that make up the PlayStation 5's PS Plus Collection can actually be played on the older console. This is thanks to a workaround which sees you redeem those select titles on your PS5, thus making them playable on your PS4 too. There's little benefit to doing this for any personal gain, but you could then theoretically hand off the PS4 system to a family member or friend with those titles ready to go if your account is set up correctly.
To activate this benefit, all you need to do is head to the PlayStation Store on PS5 and select the PS Plus Collection tab. From there, redeem all the PS4 titles you'd like to play or add to your digital collection, and then those games will now be downloadable for your profile on PS4. It's super simple so you might as well claim every one anyway.
For a full list of All PS Plus Collection Games on PS5, head on through the link. Which ones are you looking forward to checking out for the first time? Share your list in the comments below.