Magic Tree House "Merlin Missions" series
24 works, 24 primary works
In these missions, Jack and Annie have quests from the ancient wizard Merlin the Magician. These books are longer than the previous 28, and some take place in fantasy realms like Camelot. Kathleen and Teddy are two apprentices who befriend Jack and Annie during their adventures, with one of these adventures being to free Teddy from a spell. The two occasionaly join Jack and Annie and when they don't, provide them support instead.