The song on the surface is a metaphor for Katy willing to have sex with a certain person all the time. This is made blatantly obvious by lyrics such as “Pop your confetti. We can get it on [‘Pop your Perignon’ in the music video]. So hot and heavy. ‘Til dawn” and “I’ll give you a taste”, various other sexual connotations such the way she stretches out her hands on the rolling pin in the music video and subsequently caresses some other object, and additional lyrics such as “You’re never gonna be unsatisfied”, and “I’ll make it like your birthday everyday”. (Note the latter two quotes imply “devotion” to the person being referenced). In fact, the metaphor is so blatant, that it hints at the true meaning at the song, which is essentially just the negation of the surface metaphor.
The deeper metaphor is a Katy denouncing the image of her being a “devotee” to some specific person. It’s really her saying all the things in the surface metaphor in a sarcastic tone.
Take for instance the grandiose setting of the video wherein it appears as if she just spent days preparing a big birthday party. The scale is so big that it’s unrealistic, thus signalling ironic undertones. The overproduction of the audio, heavenly reverb of the vocals/guitar, high pitched keys that underline her recital of the lyrics “you’re never gonna be unsatisfied” (augmenting the soundscape with twinkling stars), and the excessive number of confections and shiny things in the video evoke a feeling of sweetness which conveys that she pleases this person to a great extent, but in fact the feeling of sweetness is so strong that it’s sickening, conveying the former (“sweetness”) statement but in a sarcastic tone (another example of this sarcasm is demonstrated by the lyrics, “big big big big big big balloons”).
When she says “So make a wish, I’ll make it like your birthday everyday”, she really means quite the opposite of what the surface metaphor would imply. Instead of it meaning that she’ll do good things (specifically, sex) for this person every day, it’s really her stating that she isn’t a slave to please this person at every moment.
The message here is disgust of the concept of a housewife. The song is founded upon feminist ideals (specifically, third-wave feminism) and contends that the idea of being dependent on a man and the implications of this (loss of sexual autonomy, house labour, etc, or – colloquially, “cock sucking”) are unacceptable and sickening.
The message of the innermost metaphor is literally, “I’m not going to tend your home while you go out to your bullshit job and hang with the bros, in exchange for your financial support. I’m not going to give you sex whenever you want, clean your mess, take care of your children, and cook your food – I can easily do the same work you do and directly support myself instead”. The song in fact seems a lot like a message of hate directed to an ex-boyfriend or ex-husband, whom she left for these very reasons. It revolts against cultural norms wherein women are basically raped by being forced into unwanted sexual encounters by proxies such as peer-pressure, economic circumstance, and patriarchal approaches of the institution of marriage.
