When I read this magazine ad (I have seen it as a billboard as well) I immediately think of the word numbnuts and there is a simple phonetic explanation for this - nuggnuts and numbnuts differ by only one phoneme and nuggnuts is not an actual word yet (and lets hope it never attains dictionary status). Additionally, it is well-known in linguistics that when the human brain encounters an unfamiliar word it will automatically search for a known word that is similar to use as a semantic template in determining the meaning of the unknown word. Because nuggnuts is not a known word the human brain searches for the closest known word and that is numbnuts.
By the way, the word numbnuts has been in use since 1970 according to Dictionary.com.
And, upon further thought, there is another (somewhat similar) word that might be used as a semantic template for nuggnuts and that is numnah. My son reminded me of this when he saw the ad because it reminded him of the humorous incident at the Scripps National Spelling Bee this past spring. To refresh your memory, one of the contestants was given the word numnah and he misheard it as numbnut.
P.S. If I were a man and I was considered by others to be a numbnuts I certainly wouldn't be proud of it.