I just saw in a pop-up advertisement, “Calling all sweettooths”. It called to mind Steven Pinkers long bit in the language Instinct on “rat-eaters” and “mice-eaters” and “sabertooths”, where the irregular plural form is stored as a separate vocabulary item, thus making it accessible rather than calling up the base word to add an -s to it. “Sweettooths” are not a kind of tooth but a kind of person.
Next, Joel, a guy that works out at my gym, a young kid, was propping a leg up on a bolster turned on end. Jokingly, I said in passing, “Don’t fall off.” He replied, “I hope to not.” Clearly not English although he is clearly a native speaker. That calls to mind the competence vs performance phenomenon where a native speaker, Joel, makes a mistake (“I hope not to FALL” or “I hope not to” would both have been OK) vs an error. A foreigner might say, “I hope to not” deriving from his incomplete competence in English; that would be an error, in SLA parlance. Joel made a mistake, in SLA parlance, b/c his competence would not only ordinarily produce a well-formed sentence but he probably realized as soon as it was out of his mouth that it sounded awkward.
BTW, I haven’t checked, but “I hope to not” could be acceptable in certain dialects.