"Hoppy's Holiday" is a fair entry into the franchise, though it has a big shortcoming--it's easy to see who is behind the bank robbery and why. That isn't enough reason not to see it, however...as even a film with a plot this thin is worth watching if it's a Hopalong Cassidy movie!
The story begins with Hoppy and his sidekicks, Lucky and California, going into town for a mini vacation. However, soon after they arrive, there's a bank robbery. California gets klunked on the head and his suitcase is accidentally switched with the suitcase with the loot in it...and folks initially think California is one of the robbers. So, it's up to Hoppy to figure it all out and bring the dirtbags to justice.
With most Hopalong Cassidy films, the time period in which it occurs is vague. A few are clearly set in the time of the old west (1870-1890) and a few, inexplicably, are set in modern times...with telephones and the like. This one is in between...with a very early car featured in the film (about 1900). But the funny part of this is seeing the baddies driving out of town in this early jalopy. It's funny because they traveled at about 10-20 mph (or less), tended to break down easily AND could only travel on smooth roads....and you could practically catch up to them by jogging!
Overall, a decent film but as I said above, it's pretty obvious who is behind this mess. Entertaining but slight. And, IMDB trivia is interesting with this one, as Ellen Corby (Grandma on "The Waltons") co-wrote this one...as well as one other Hopalong Cassidy film!