Ben, The Doctor and others in “The Power of the Daleks”

Ben

The Doctor always wore this. If you are him it should fit... That settles it!

I'd like to see a butterfly fit into a chrysalis case after it spreads its wings.

Polly

Then you did change.

Life depends on change, and renewal.

Ben

Oh, that's it, you've been renewed, have you?"

Renewed? Have I? That's it, I've been renewed. It's part of the TARDIS. Without it I couldn't survive.