The song was received positively by music critics upon release, who commented on the composition, the participating musicians, the B-side "Dust", and its cover art.

Advancing from the album, he wanted to ignore small details and focus on doing exciting and fun projects, which led the production process of "Gag" and its B-side "Dust".

[4] At a later film release event, Hoshino said that he created the song with respect to the production team that backed him and co-star Mirai Moriyama, voice of Jesus Christ, during recording.

[6] Other musicians participating on the track include drummer Daichi Ito [ja] (co-member with Hoshino in the band Sakerock) and keyboardist Takuji Nomura.

He wrote that the track's "fun" swingy rock and roll musicality covered part of its honest theming, which he believed was commentary on the tempo of anime and manga.

[3] Emi Sugiura, also for Rockin'On, praised the guitar phrase of Nagaoka on the track as strangely distorted yet warming, which she thought provided for an effective hook to the tempo.

[18] Satoshi Takagi for Real Sound named the single's cover art as one that would increase customer interest, praising its illustration and humor for helping showcase the song's poppy funniness.

[12] Tied with Maximum the Hormone's album Yoshū Fukushū, the cover art was a runner-up for the Grand Prix at the Recording Industry Association of Japan (RIAJ)'s 2014 Music Jacket Awards, beaten by Miwa's Delight.

[2] Koike praised the track as "amazing", writing that its scales remind of the Buddha and gives a feeling of Buddhist reincarnation / saṃsāra through a "soft touch" of blue funk.