You can get muskrat at the local fire department fundraiser and even the occasional restaurant on the Eastern Shore of Maryland in the wintertime. That said, I have never eaten the tongue of anything...Maybe I have been missing out.
Many years ago while living in Montana I was going to try muskrat. Went out on the river and shot about 10 as I recall. Took them all home and left them in the back room while I went in and warmed up some. Went back out after a bit and it looked like a bunch of rats had died out there. Threw them away! But I'd bet they are not to bad, they are vegetarians I think!