The Ticking Clock seems to take place 1 year after Phineas and Ferb: Summer Belongs to You! (2010) because Summer Belongs to You has the 27th annual substitute teacher awards, and The Ticking Clock has the 28th annual substitute teacher awards.
The song playing on the radio which guides the ponies onto Milo's roof is "Everything's Better with Perry," from the 'Phineas and Ferb' TV Movie.
Milo plays the accordion in the band. "Weird Al" Yankovic, who voices Milo, is well known for playing the accordion in his music career.
Although This Episode Premiered In 2019 It Was Made In 2018 According To The Credits