Reddit took a chapter from Google’s book: customizing their logo for special occasions. The Reddit logo now includes a ball and the Italian flag…
Update (7/9): Alexis, Reddit’s cofounder pointed out while the original idea came from Google, they are now in the habit of making event-driven custome logos regularly. Thanks for the comment, Alexis. 
Thanks for noticing 🙂
You’re right, Google was certainly the inspiration, but nowadays we’re beyond just holidays and events, doing it almost every weekday.
Wow, I haven’t noticed before… I wonder how many Reddit-ers have. Thanks for the comment, Alexis, I’ve updated the post.