One summer I came home from a fair with 5 or 6 helium balloons. I tied them all together and then started adding weights. I tied on some sticks, a Star Wars figure, a couple green army men and other stuff I found. I kept experimenting until I found the right combination to achieve neutral buoyancy. The whole thing would float in the middle of the living room at whatever altitude I would put it in. I took it outside and paraded it around the neighborhood like some sort of pet. I had a yard stick with me and I would give it a little push and it would float out ahead of me. I would catch up and push it off in another direction. I was walking down my driveway when the wind took hold of it and slowly sucked it straight up into the sky. I stood there watching it thinking and second now it will come back down. Some 25 or so years later I still wonder if anyone ever found it.