xkcd comic where a bald stickman (Person1, pressumably male) is walking up to the open door leading to a medium length haired stickman's (Person2, pressumably female) apartment
(First panel)
Person1: "Hey, I was wondering if you had plans for-- Holy crap, what happened to your apartment?"
Person2: "I filled it with playpen balls!"
Person1: "I... What? Why?"
(Second panel, from the point of view of Person1)
Person2: "Because we're grown-ups now, and it's our turn to decide what that means."
In the third panel Person2 is out of frame and Person1 is seen staring at the ball-apartment, then in the fouth panel he's out of frame too, the balls are spilling out of the door and a pink heart is flying out of the room
I imagine it would be quite fun for a while, but that the novelty would wear thin about the time you woke up in the middle of the night to use the bathroom for the first time.
Filling a basement den with them, though... lounging in a sea of balls while watching TV or something... I am not seeing the downside.
I mean you couldn't snack while in then - too much risk of crumbs and it'd be difficult to clean with them all around so risk of bugs. I guess you could just vacuum blindly !