Oliver has started laying on the recliner a lot. The Boy has started tucking him in under the TARDIS blanket. Naps are bigger on the inside.
But sometimes a kitten gets a little peckish and has to leave the TARDIS for a snack. If The Girl doesn’t notice and make a TARDIS cave by pulling the blanket tight over both arms of the chair, the kitten has to make do by sleeping on top of the blanket.
It’s big enough on the outside.
Kitten Thunder: Life lessons and cat tales 
Awwww. I was going to suggest that you fold the blanket over him, but then he’d be inside an inside-out TARDIS, and I’m not sure what would happen to space and time in that case.