Are there any rules for forming the plurals of loanwords?
I ask, as I was recently reminded of a sign I saw in an Office Depot in Mexico advertising "mouses".
Can this be correct in Spanish, or is it proper form to use the English plural "mice" in this case? If "mouses" is proper in this case, are there other examples where the plural form is also borrowed from an original language, but the Spanish plural would be considered incorrect?
NOTE: I know we're guilty of the same class of error in English, when we talk about a single tamale.