"Back Door" by Stray Kids is a song that talks about the excitement of partying and being together with friends who share the same interests and passions. The song starts with Felix's invitation to come in and join them. The lyrics emphasize the need to let go of worries and enjoy the moment to the fullest.

The first verse highlights the idea of a real party that has just begun, and even if someone is not comfortable with it, they can pass it and watch others enjoy the night. It talks about freeing oneself and enjoying the event by keeping eyes open all night.

The pre-chorus speaks of stretching out and facing our wishes. The chorus repeats the phrase "If you ain't with us, you can't pass the back door," implying that only those who share their passion and interests can join them in the party. It encourages people to come inside if they want to be part of a group with similar interests.

The second verse indicates the end of matching with others and the readiness of the members to go. It tells us not to worry as we hear sounds of fanfare and that it is okay to spend all night playing and having fun. The lyrics suggest that it's imperative to use the secret password "Open Sesame" to enter the party.

The bridge urges the listener to open their eyes, record a memory burn-in in their mind's eye, and feel the beat pumping through their bodies. The post-bridge emphasizes making everyone say wow, wow, wow, and calling all others to come and join them.

The chorus repeats, indicating that only those who share the same passion can pass through the back door. The post-chorus encourages everyone to ring the bell and go wild while repeating "We do our thang" and "All night." The song closes with Felix's invitation to come in.