War Rhinoceroses?

I'm pretty sure you're thinking of 'To Kill a Mockingbird' I remember the scene with Atticus Finch in the courtroom with the Rhino very clearly.

I'm surprised that you've neglected to mention the German Big Bertha gun used in 1918 to fire shells containing live Rhinos into the city of Paris in order to sow panic and confusion. Despite being a military fiasco, it inspired the Eugene Ionesco play 'Rhinoceros', in 1959, which in turn was made into a movie of the same name starring Zero Mostel and Gene Wilder, in 1974, and inspired the Canadian political party of the same name in 1979 (the only major political party in a western democracy to be lead by an actual rhinoceros).

And that Rhinoceros got his start in education, as principal of Flying Rhino Junior High.
 
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