How can I add a secret link easter egg in my game?

I will make it short, I've got two projects on my plate. One is pretty easy, while the other is a spooky Halloween special that's seriously challenging. Now, here's the question: How can I show the player a link to the Halloween special one? Maybe a pop-up page could do the trick if that's even possible when they do an action?

In one of the older Jam announcements I used a 'click link'. Hope it's of any help.

https://microstudio.dev/i/TinkerSmith/msjam3/

This is the part in question:

    if mouse.press then
      system.javascript("window.open(\"https://itch.io/jam/microstudio-jam-3\", \"jamlink\");")  
    end

Thank you very much, this should do it!

Edit : I adore you so much