I
Icecream
Cold, but goooooood!
Impersonator
Intelligent humans try harder than the others to be like cats.
Inside
Cats like to be inside things. Humans seem to have opinions about this. If they didn't want us to be inside things, they should not make so many things exactly the right size to be inside of.
Inspect
New humans must be judged, lest they be found wanting.
Ironing board
Ironing boards are lightly-padded high places, just the right width for cats to sleep on.