Fast forward to last night. We went out to Red Robin (long story) for dinner, and on the way out I got a pretty green balloon. Unfortunately the string was too short for the kitties to reach easily, but it was fun watching Heidi jump and try to get it.
Overnight the helium wore out and, when I woke up this morning, the balloon was in our room. I pointed this out to Andy, and he said "Aw", and we both went back to sleep. When we got up for real, the balloon was back in the living room. Later in the day I determined that the primary (and perhaps the only) balloon mover is Heidi, who gleefully bats it around.
Her manner of moving it around doesn't surprise me. Sean has taken over as our string kitty, loving to drag things around by means of thin pieces of fabric/plastic. Since neither kitty appears intent upon popping the balloon, I'm still suspecting that Sean will get around to doing some redecorating of his own, hopefully when I can get a picture. Silly little guy has become camera-shy.
And, since I've mentioned three of our kitties in a post, here's a link to pictures of the first one, Thena, who only ever played with bubbles. Or rather, she may have batted around balloons post-helium, but if so I don't have the pictures online.