* BoxOfficeBomb: ''Willard'' only made over $6 million (with an additional worldwide gross of over $1 million) against a $20 million budget.
* BreakawayPopHit: Music/MichaelJackson's performance of "Ben" (which was written for the original movie's 1973 sequel) is probably more popular than either the book or the two movies.
* CompletelyDifferentTitle: The film's Spanish title is ''La Revolución de las ratas'', meaning "The Revolution of the Rats".
* KeepCirculatingTheTapes: The book was out of print for decades until finally being reprinted in 2013 by Valacount Books.
** The 1971 movie was also this until 2017 when Creator/ShoutFactory finally released it on Blue-ray and DVD. The film can now also be easily viewed on multiple streaming service, too.
* MoneyDearBoy: According to Creator/ErnestBorgnine's autobiography, they offered him a choice of a higher salary or a percentage of the box office. Borgnine chose a higher salary.
* ReferencedBy: The novelty song "The Cockroach That Ate Cincinatti" includes the lines "''Willard'' just sent me out laughing / I thought ''Ben'' looked a little bit ratty.." The singer gets some [[LamePunReaction on-air disapproval]] for that second line and apologizes.
* RomanceOnTheSet: Bruce Davison and Sondra Locke were dating in real life at the time the movie was made in 1970. They were never together publicly as a couple because Locke was married.
* {{Typecasting}}: Creator/RLeeErmey more or less reprises his role as [[Film/FullMetalJacket Gunnery Sgt. Hartman]] as a BadBoss.
* UnderageCasting:
** In the original film, 27 year old Willard was portrayed by then-24 year old Bruce Davison.
** This got [[DawsonCasting inverted]] in the 2003 film; Creator/CrispinGlover was almost a decade older than his character at the time of filming.
* WhatCouldHaveBeen:
** In the 2003 remake; there's an alternate ending which is true to the source material. In the alternate ending, Willard is instead overwhelmed and consumed by the mischief of rats while Ben looks on.
** Creator/BruceDavison suggested that for the sequel, Willard would return, alive but disfigured and living in the sewers, still commanding his rat army. The studio passed on it, deciding instead to make the aptly named ''Ben'', which focused on Ben.
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