According the the Hardy Boys Wiki she makes her 1st appearance on page 8 of Book #45 (the Mystery of the Spiral Bridge)
Henry Kurt is in book #33 (The Yellow Feather Mystery) in the Hardy Boys series
The cast of Ambitious Ethel - 1916 includes: Oliver Hardy Ethel Marie Burton
#1 The Tower Treasure was adapted for the Applegate TV season, and he is mentioned in While the Clock Ticked
Frank and Joe Hardy are the heroes in the Hardy Boys series. They are brothers who are amateur detectives and solve mysteries in their hometown of Bayport.
The cast of The Other Girl - 1917 includes: Oliver Hardy as Babe Ethel Marie Burton as Ethel Florence McLaughlin as Florence
The cast of The Love Bugs - 1917 includes: Joe Cohen as Cohen Oliver Hardy as Babe Ethel Marie Burton as Ethel Florence McLaughlin
The cast of This Is Not My Room - 1917 includes: Oliver Hardy Ethel Marie Burton
Frank and Joe Hardy.
The cast of Fat and Fickle - 1916 includes: Oliver Hardy as Babe Ethel Marie Burton as Ethel Florence McLaughlin as Florence Kate Price as Kate
The cast of He Winked and Won - 1916 includes: Oliver Hardy as Babe Ethel Marie Burton as Ethel Florence McLaughlin as Florence Kate Price as Kate
The cast of Chickens - 1916 includes: Bobby Burns as Jabbs Frank Hanson Oliver Hardy Ethel Marie Burton as Ethel Gotrocks Walter Stull as Pokes
In the Hardy Boys series, created by Edward Stratemeyer, Frank and Joe Hardy do not die. They are fictional characters who star in a long-running series of mystery novels for young adults.