Original 'Willard' still not on DVD, unfortunately. Rights problems, I hear.
The film enjoyed a healthy run at Hoyts' drive-ins...
and a Melbourne city cinema, too, 'The Athenauem' on Collins St. (now a legit theatre)
Interesting to note how many suburban drive-ins Hoyts ran in the 70's. In the metro area, only the Coburg Drive-in still exists. It is a triple-screener and is now operated by Village, Hoyts' competition. The famous Dromana Drive-in still operates on the Mornington Peninsula. It is independently owned.
The 'Willard' novel by Stephen Gilbert, originally published as 'Ratman's Notebooks' (68), is an excellent read in the first person.
Was James Herbert's 'The Rats' ('74) inspired by it to any extent? Perhaps. Although 'Ratman's Notes' is not an Animals Attack novel, its subject is still a ripe one for inspiration.
The film sequel to 'Willard' was 'Ben' ('72), which spawned a hit theme song by Michael Jackson, who would probably enjoy the company of four-legged things that squeak.