Three balloons. Daddy balloon, mummy balloon and baby balloon.
Daddy balloon said to baby balloon, "Look son, you are getting much to old to sleep in mummy and daddy's bed, you will have to sleep in your own bed".
Baby balloon protests, "I like sleeping with you and mummy".
"No, you are not sleeping with us and that's final" said daddy balloon.
"Ok then" said baby balloon sadly.
Two in the morning, baby balloon wakes up and decides to climb into bed with mummy and daddy. He finds there is not enough room, so he unties his daddy's knot and lets out some air, and ties him up again. Still not enough room, so he unties his mummy's knot, lets some air out and ties her up again. But he still can't get in, so he unties his own knot, lets out some air, and ties himself up again, he finally has room, and snuggles down with mummy and daddy.
The next morning they all wake up, and daddy balloon is really angry. He said
"Son, I am really disappointed with you. I said you can't sleep in our bed, but you ignored me. So you've let me down, you've let your mummy down, and worst of all, you've let yourself down. 
