That rap's been foister unto us rats for years. Rats are not dirty! Just like snakes are not wet and slimy.
7 seconds sound clip from the The Brave Little Toaster to the Rescue movie soundboard.
You can hear this line at 00:05:14.247 in the Blu-ray version of the movie.
Quote context
[...]
- Well, pardon my breathing, Little Miss Princess!
- Hey! That is quite enough, Ratso. You are not, as they say, very respectful.
- Little Alberto. Looks like a dog. Sounds like a dog, only he's too small to be a dog.
- You stop that! You... You dirty rat, you!
- Absolutely, positively correct, Ratso.
- I'd recommend steering clear of words with too much s-s-sibilance, pal.
- Now look what you've done. You woke Sebastian.
[...]