As usual, I'm probably the last person on the planet to see this movie. But on the off chance you haven't: it's very funny, and has an inventive premise, which is adequately captured in the title.
Aside from the premise, it's pretty predictable. All these movies have the point where things are going swimmingly, then it all comes crashing down around our heroes, seemingly irretrievably. It's here too! Old dotty person saying outrageous things? Check! Heroine cannot detect that her boyfriend is a horse's patoot, a fact obvious to everyone else? Check!
Nevertheless, things are still fun to watch even when you see them coming.