I just found a very old Mr. Mugs book. Mr. Mugs was a sheep dog who starred in a series of books designed to help young children learn to read. I had several as a young child and even read them in kindergarten. It's fair to say Mr. Mugs had a huge role in teaching me how to read.
Surprisingly, there's very little about Mr. Mugs on the Internet. Is Mr. Mugs that obscure a reference? I assumed most children learning to read in the late 70s would have the same attachment to this mutt that I have. Apparently not.
Here's a scan of the cover and another page from the copy I just found. You know it's dated by the fact the second picture shows the dad smoking a pipe. Try and find someone smoking in children's reading books used in schools today. Let me know if you remember Mr. Mugs fondly or if I'm the lone member of this shaggy dog's fan club.