As long as you are not doing anything dangerous or illegal it's fine.
My best friend and I have been using secret codes for over 20 years, since we were nursery age.
I have an amazing best friend. I've known her for about 4 months, and we gradually just got closer over time. Like any other best friends, we have a hell of a load of inside jokes, and let's just say we can be very weird. We're both 17, but I feel like sometimes we can act like 2 year olds. I'm very aware that we do get judged about how we act around each other, simply because we both just lose the plot, or just communicate non-verbally or just playing or arguing (playfully) about pointless things. We do get told that we are very weird. Like today, we were just talking in a different accent, and we got a couple you're weird comments. Is this normal?