App icons can be changed in settings > app icons menu. This time Reddit got 4 new themed icons where one of them is available for free. Normally, alternative icons are available for premium users. "Rocket", "To the moon", "Wall Street", "Stocks" - are references to the popular "r/wallstreetbets" movement where Redditors team up to trade stocks for fun via no commission trading apps like Robinhood or Trading 212.
Interesting note: Recently, "wallstreetbets" moved to Telegram and their group was the first to reach 1000 online participants in the voice chat. Afterwards, this limit was increased to 5000. Currently this group has more than 100k members.