Do you know what an ambigram is? It is a word that spells the same thing right side up or down. A symbiotogram is a word that spells one thing right side up, but when flipped spells an entirely different word.
Here is an example of a symbiotogram:
Each word "Ryan" and "Kate" spells the other when it is flipped.
If you think your kids might have fun with this concept, you might want to check out the online ambigram generator. (It does symbiotograms too, but they have to be words of the same length).
I think ambigrams and symbiotograms have all kinds of creative potential. For example, when I was a middle school Latin teacher, I used to create symbiotograms using Latin words and their English definitions. The kids had fun figuring them out! Certain kids were inspired to create their own word tricks. Interestingly, the activity seemed to be an especial hit with a couple of my students with Asperger's Syndrome.
If you do anything interesting or fun with the ambigram generator, I'd love to hear about it!