There’s an old saying: “Every goodbye ain’t gone,” meaning just because someone bids farewell doesn’t mean they are out of your life.

If this were an encyclopedia entry, the accompanying illustrations could be of Peter and Emma in the somewhat amusing romantic comedy “I Want You Back,” debuting Feb. 11 on Amazon Prime Video. These are two people just dumped by their significant others who, instead of meeting cute, meet sad while licking their respective emotional wounds in a workplace stairwell. As they tumble through the five stages of romantic grief, at first there’s resignation (“Dying alone is not such a bad thing”) but, ultimately, they are not about to suffer this indignity simply by smoking and stress eating Cinnamon Toast Crunch, though there is some of that.

Peter (Charlie Day, “It’s Always Sunny in Philadelphia”) and Emma (Jenny Slate, “Bob’s Burgers”) concoct the kind of plan that could only ever possibly work in the twisted logic of a romantic comedy. She will seduce Logan (Manny Jacinto), the arty hunk who caused Peter’s ex (Gina Rodriguez) to leave him, while he will become best buds with and a wing man for party-hearty personal trainer and all-around stud Noah (Scott Eastwood), Emma’s ex who left her for the entrepreneurial Ginny (Clark Backo), the owner of a healthy, trendy pie shop. If Peter and Emma can get back at their old flames by proving their new partners are unfaithful and unreliable, the strays will come running back home.

Sounds like a plan, right?

There are some fun moments in “I Want You Back,” with Day bringing some of that same nervous, nebbishy energy he displays in “It’s Always Sunny in Philadelphia,” and there’s a genuine chemistry among the four leads. Pete Davidson makes a cameo appearance that is pure Pete Davidson.

Yet director Jason Orley (who directed Davidson’s “Alive From New York” TV special), working from a script by Isaac Aptaker and Elizabeth Berger, gives us a bit too much of a somewhat good thing. At just under two hours, “I Want You Back” goes on too long, wearing out its welcome before coming to an end that can be seen coming several miles away.

但是,在低迷的时刻,你总是可以倒yourself a nice, big bowl of Cinnamon Toast Crunch with freshly refrigerated milk to mirror the film’s message that revenge, indeed, is a dish best served cold.

cary.darling@chron.com