It's just a rabbit with a waistcoat... and a watch.
5 seconds sound clip from the Alice in Wonderland (1951) movie soundboard.
You can hear this line at 00:05:00 in the Blu-ray version of the movie.
Quote context
[...]
- There'd be new birds, lots of nice and friendly howdy-do birds
- Everyone would have a dozen bluebirds within that world of my own
- I could listen to a babbling brook and hear a song that I could understand
- I keep wishing it could be that way because my world would be a wonderland
- It's just a rabbit with a waistcoat... and a watch.
- My fur and whiskers! I'm late, I'm late, I'm late!
- This is curious, what could a rabbit possibly be late for?
- I'm late, I'm late for a very important date. No time to say hello, goodbye. I'm late, late, late.
- It must be awfully important, like a party or something.
[...]