I love this.
dialogue from my 2nd year french class:

--"what's the plural form of 'pluit'?"
--"it doesn't have one."
--"why doesn't it have one?"
--"well, I guess technically it kind of could be conjugated with plural endings - but you'd never use it because it's only ever used as an impersonal verb, which can only be singular."
--"what do you mean?"
--"people only ever say 'it is raining' - you'd never say 'they are raining'."
--"well, you could say 'the kings are reigning.'"
<<french teacher shakes her head and walks off without another word>>
CM Adams 2/4edited