Dear Professor McGonagall,
Can cats see through invisibility cloaks?
Francesca of Hufflepuff
I will assume your question is one of intellectual curiosity – or that you have the potential to assume cat form as an Animagus – in which case, you should make an appointment with me to discuss this advanced Transfiguration topic and to arrange tutoring.
To address your question from the intellectual standpoint, however… The standard Demiguise cloak is subject to detection by a variety of means, including a summoning spell, and a witch or wizard hiding under it is certainly vulnerable to discovery by the average familiar, including cats, as well as by nearly any Animagus.
If you are inquiring about the Cloak of Invisibility legend attributes to the possession of Ignotus Peverell and his descendants, however, of this, we have no knowledge, though one would assume that, as the subject of legend, it would have extraordinary powers and be near infallible. Again, however, this is the subject of legend and children’s tales, as anyone familiar with Tales of Beadle the Bard can attest.
Again, if you are contemplating the Animagus transformation, please do not attempt this on your own, and see me to arrange a tutorial.
Hogwarts School of Witchcraft and Wizardry