Twice the Fun?
As you parade your new twins through public places, passers-by will seem compelled to somehow acknowledge the fact that you have not one, but two, infants in your care. Your outings will always (not sometimes, always) be peppered with succinct little "salutes" from well-wishers. Despite their undoubtedly kind intent, they may become annoying when combined with the tens of other well-wishers who've offered the very same greetings ... over and over and over. Adults do say the darnedest things ... and they tend to plagiarize each other, so be prepared. And try to be flattered.
If I've heard it once, I've heard it over two hundred times. That is no exaggeration. Don't let this one get you all hot under the collar. The individual tossing out the world's shortest poem was probably grinning jealously as he/she said it. Of course, your babies aren't "trouble." Even if at the present moment you believe they are, you sure don't want to reveal that to a stranger, and certainly not in front of your children.
The reality is you're commandeering a special twosome. You have a special role; one that not everyone has the opportunity to fill. Many, if not most, are daunted and awestruck at the mere thought. Folks want to acknowledge you somehow. Let 'em do it.
As far as the literal meaning goes, ignore it. Let's face it, we all like rhymes. From nursery rhymes to off-color limericks to rap music, the aural appeal of rhyme is undeniable. Take solace in the knowledge you will hear "Twice as Nice" from the more thoughtful poets passing by.