Bill & Ted’s Excellent Adventure is a typical time travel film with an unoriginal plot but was super successful.
Bill (Alex Winter) and Ted (Keanu Reeves) are boneheaded high school students, one day when they are struggling with their history report, a person from the future comes and gives them a time travel machine (what else, but a phone booth). They travel around the world to bring back various historical figures with them from the past to present on stage. In the climax, we are shown a lame excuse on why the people from the future want to help them.
The film was fun to watch if you don’t think about why and how!