[2] A few weeks later, the band posted a cryptic URL which allowed users to unscramble the word "NUMB," and would receive a musical snippet upon doing so.

The fourth single, "You'd Be Paranoid Too (If Everyone Was Out To Get You)", was released on April 28, 2021, sharing its title with an autobiography written by vocalist and rhythm guitarist Awsten Knight.

[9] Despite heavy involvement with the production of previous releases,[10] Greatest Hits is the first Waterparks album for which Knight is explicitly credited as a producer.

[20] Matt Collar of AllMusic was positive and considered to songs on Greatest Hits to be "stadium-sized singalong anthems".

[19] Writing for Upset, Stephen Ackroyd described the album's sound by stating, "never anything but in your face, it switches from pop-punk to full-on hyper-pop banger at will.

Emily Carter described the album as "wildly experimental" and Awsten Knight's work on it as having "emphatically succeeded in being the polar opposite of dull".