Semi-serious suggestion:
Emoji based quote codes. There are 3,300 emojis so four characters gives billions of possibilities. We parse quote codes into the alphanumeric code (on the back end of course)
Your quote code is: "🎉🙀🎺🦍"
The serious part is, can it handle character sets other than the ASCII characters it has been tested with so far.
Semi-serious suggestion:
The serious part is, can it handle character sets other than the ASCII characters it has been tested with so far.