They are: Serendipity, The Dream Tree, Wheedle on the Needle, and The Muffin Muncher.
To date, there are 70 books in the series, written from the kindergarten to grade three levels.
[1] The animals in the Serendipity series include bears, cats, dogs, horses, squirrels, rabbits, and mythical creatures such as unicorns, dragons, sea monsters, and pegasus.
The books present moral issues such as growing up, disabilities, abuse, fear, friendship, prejudice, gossip, fat shaming, and helping the environment.
At least 25 of the books were translated into Spanish (based on the list in El Dragon Gloton) and at least 6 in Italian (by Arnoldo Mondadori Editore).