With original credit to Doorknob for providing the picture, I can confirm that the heart shape is indeed real (unlike the chickens, those were a troll by Telkitty).
Thanks to THelper suggestion, I can confirm that the trigger seem to be related to clicking (on the head?) of the stick figures: doing that, I was able to trigger the heart formation multiple times.
When the stickmen start forming the heart, you will notice they suddenly stop fighting each other.
I think to also know why this egg was added.
When the countdown to winterbash started, the site just contained a dark background, with the stickmen running around to form the numbers of a countdown.
Then, one use posted this question: How do I interact with people?.
I'm afraid I'm a little shy, and it's hard for me to find the right way to interact with the people.
That said, I've tried several things, and nothing is working.
For instance, when I click on one of them, they don't seem to notice. Waving the cursor over them doesn't alter their behavior either. Clicking and dragging yields no response.
I bet that balpha took the idea from there and decided to add something that would be triggered if someone tried to interact with these small ones.
... now, why he didn't take my suggestion to replace those humans with some unicorns I don't know...
