Simply referred to as the "Red Headed Boy" in Lucky Lucky,  he's always a bit sad. Sometimes legitimately, when someone (Lucky) steals his wish, and other times for something as simple as spilling milk or dropping his ice cream cone.

Evil Professor DeLeon makes an appearance in Smarty Pants, and is very interested in Charlie's Smarty Pants that make Charlie super smart.  

The Genie plays a big role in the book Lucky Lucky.  Be careful what you wish for with her, because things never turn out exactly the way you expect.

Rose makes appearance in both Val's Day, sitting on the park bench with Charlie, and plays a big part in Dance Pants - but Rose will be having some of her own adventures, someday.

Stanley makes appearances in all three Charlie's Adventures in Pants book, as the younger brother of Charlie.  Stanley is fun and supportive - who could ask for a better baby brother?

Gertrude is Val's best friend in Val's Day.  While she would never want to hurt her best friend, she's destine to fall in love with Val's true love, Belly.