Pitchfork wrote that "Happy" might be one of Mitski's bleakest songs yet, and further wrote "Mitski resists psychic death by constantly pushing forth into bolder textures, refusing to be meek and sedated even as joy feels compromised: a stubborn drum machine begets chuntering percussion, the tentative melody finds its feet, and brash saxophones push everything up a gear."
AllMusic considered the song to be one of the highlights from
Puberty 2, writing that it's "full of bite and irony as she describes a hook-up and his stealthy exit in a context of grooving rhythms, a catchy melody, and poppy saxophone solos. Through it all in the background -- though it's brought to the fore in the intro and outro -- is the relentless pounding of a drum." ==References==