Moved to Neopets Chat.
Welcome back. One big change is an annual (last 2 years) even called Charity Corner. You exchange 5 items of a certain type, like school, clothing or toys, for a random one. If you do 5 r90-r99s, you get 1 random r90-99. It affected the economy quite a bit.
Birthday cupcakes changed BD pets. Can adopt a pet on its birthday, get a cake that gives +5 to str, def or HP, then pound. Repeat every day for easy stats.
(you need an account to see links) This petpage gives a summary of changes made every year, which might be useful for you to look at.