We knew Ben Affleck and Jennifer Lopez could make bad movies separately, but “Gigli” demonstrates that, in a true example of synergy at work, their combined efforts can generate even more badness.

Larry Gigli (pronounced “Gee-lee”) is the name of Affleck’s character, a Jersey-born mid-level thug who works for mid-level crime boss Louis (Lenny Venito) in Los Angeles. Larry’s latest assignment is to kidnap the mentally handicapped younger brother of a federal prosecutor who’s been making trouble for Louis’ boss, in the hopes of getting the guy to play ball.

But since Larry has a penchant for screwing up Louis’ assignments, he is given a partner to keep an eye on him. She is Ricki (Jennifer Lopez), a stunning woman whose clothing always accentuates her greatest asset, who is extremely well-read and knowledgeable about psychology, and who also is a lesbian. This frustrates the ultra-macho Larry, who can’t conceive of a woman unwilling to sleep with him, let alone one smarter than he is.

And so they hole up in Larry’s apartment, taking care of the kidnapped Brian (Justin Bartha) and awaiting instructions from Louis while Larry makes irritating attempts at converting Ricki.

As you can see, the film is already fraught with peril. Ben and J-Lo have their various charms, but neither is much good at acting. Consequently, Affleck is not convincing as a Jersey tough-guy, and not once did I believe Lopez as a lesbian, a hired thug, or a person who knows big words. The acting is not bad, per se, just wrong. More blame should be placed on the director, Martin Brest (“Meet Joe Black”), for miscasting his leads, or on the writer, who is also Martin Brest, for penning such pointless, meandering dialogue.

There is also the matter of having a mentally handicapped character featured so prominently. Bartha’s performance does not cross over into “making fun” territory, but it does teeter awkwardly on the line between being funny and being sad. One doesn’t know how to react to him, which often makes viewing the film uncomfortable.

Taken as a whole, though, the presence of a difficult character is the least of this film’s problems. This is a movie that manages to keep finding new ways of being stupid, from the forced (and rather insulting) romance between Larry and Ricki, to their crass conversation about the relative values of the male and female genitalia, to the hilarious way soft music cues indicate when we’re supposed to be touched by Brian’s innocence, to Al Pacino’s one-scene foray into outrageous over-acting (a realm he is not unfamiliar with, of course). I will also mention a brief glimpse of Lainie Kazan’s thong-clad rear end.

On a more positive note, there a brief appearance by the ever-insane Christopher Walken, who brightens any film merely by entering it.

In the end, “Gigli” wants us to feel good, but that is hopeless. The plot is minimal, leaving us to watch the characters just sit around being themselves — a bad thing, since they’re all either dull or unlikable. This is a movie all about relationships and connections between people, and none of the relationships or connections come across believably. I hope Ben and J-Lo are doing a better job relating to each other in real life, or else there’s serious trouble ahead.

D (2 hrs., 4 min.; R, nonstop harsh profanity, some explicit sexual dialogue, a brief scene of sexuality, brief strong violence.)