What do you call a group of killer whales playing instruments?
Why this joke works
Killer Whales Make Music
An orca is another name for a killer whale, while an orchestra is a group of musicians playing together. The answer squeezes the animal's name into the musical word. The setup supplies both halves without saying either key term outright. Say the answer as one flowing word, rather than spelling out its pieces, so the imaginary underwater ensemble arrives in a single beat.
A closer look
A name for an imaginary ensemble
This is a naming riddle rather than a claim about animal behavior. The whales are given a human activity, and the answer supplies the label that would suit their fictional band. A listener needs both the word orca and the idea of an orchestra; a picture of a whale alone cannot supply the missing musical vocabulary.
Fact behind the joke
A whale in the dolphin family
Despite its common name, the killer whale belongs to the dolphin family and is its largest member. Orca and killer whale therefore name the same animal, not two different performers. That naming fact supplies the otherwise hidden animal word inside the punchline.