If you are near Minnesota check out the Earth World exhibit at the Minnesota Children's Museum in St. Paul which includes the chance to crawl into a muskrat lodge. (Recommended especially for children 4 to 8 years of age.) Phone: (612) 225-6000/TDD: (612) 225-6057
Strange but true, muskrats have inspired some music. There's Muskrat Love by The Captain & Tennille (late 70's) and The Muskrat Ramble. You can download the Muskrat Ramble played by the MATC Municipal Band in Rome from the MATC Net Talk page.
Wildlife claims to be a comicstrip about a muskrat named Carson, but it sure doesn't look like a muskrat.
Mortimer Muskrat (gif) is an albino. (He narrates a children's guided tour of the J. Clark Salyer National Wildlife Refuge's Canoe Trail.)