The spells *Phantasmal Force* and *Major Image* allow you to create the illusion of a creature, here for example the text from *[Major Image](https://www.dndbeyond.com/spells/major-image)*:

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> You create the image of an object, a creature, or some other visible phenomenon that is no larger than a 20-foot cube.
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This explitly refers to "a" creature, in singular. How does this work with a swarm, for example the [swarm of rats](https://www.dndbeyond.com/monsters/17032-swarm-of-rats), which is a single monster. Does the spell allow you to create the illusion of such a swarm?