The plural of 'passerby' is 'passersby' with an 's' acting like an infix (W-B says that this is the only plural form of the word). This seems like a very interesting exception, so I thought I would ask a question.
Are there any other English words that are made plural by an 's' put inside the noun?
One criterion has to be met: the singular noun is composed of one (unhyphenated) word only.