I think this is an anti-advertisement system than an easter egg.
There are hacked clients that send messages to people in the hub. Memeplex has it and I got muted there because I was "infected" by it.
The way it works is simply that it puts in letters and presses tab so it searches for players. Just like
@hgbf said, it doesn't have to be "duck". It can be "banana", "orangejuice" or just "sdmqlkfjqmskjfq".
It's complicated, I now, thanks, lmao.