Like “Roar”, this song is a return to the upbeat sound of Perry’s early work, and after two more dreary attempts as ‘seriousness’, that certainly comes as something of a relief. But the fact remains that this is an incredibly stupid song (it’s basically a distaff version of Jeremih’s infamous “Birthday Sex”). Granted, some of the songs from Perry’s early career were equally stupid (“Hot N Cold” being one obvious example), but those songs were also extraordinary catchy, which helped elevate their idiocy into the realm of the enjoyably bad. By contrast, the melody of “Birthday” is only moderately catchy, and not really enough to compensate for its gaping flaws.
Verdict: Perry’s done worse lately, but this is still pretty bad.