Young F got this jewel in his cracker yesterday:

Q: What kind of relationship does coral have with algae?
A: A symbiotic relationship.

Now, this answer turns out to be perfectly sound biology (so I at least learned something) but doesn’t seem to me paticularly funny. Am I missing some point about, perhaps, two popular celebrities or fictional characters called Coral and Algy? Or is it just meant to be funny because coral is generally hard and algae generally squishy?