The veteran actors portray a couple who marry after 39 years together in the Ira Sachs film that premiered Saturday at the Sundance Film Festival.
Once wed, one of the men loses his job as a music instructor at a Catholic school and the couple is forced to sell their apartment to survive financially. They end up living apart, staying with friends and family until they can remedy their situation. All the while, the couple comforts each other and has fun together.
"What I feel is really a success of the film," Sachs said, "is that these two men create the history of a 40 year relationship with all the texture."
Lithgow and Molina have been friends for 20 years but this is the first time they have worked together.
"I just knew this was going to work so wonderfully," Lithgow said. "I knew we were going to be a great old couple."
"So much of this grew out of Fred's and my old friendship," he continued, "and the things we discovered, the layers of new friendship."
The actors received a standing ovation at the conclusion of the film's premiere.
Sachs, who acknowledged his husband before the screening, said the film is autobiographical "only in emotion, and not in fact."
"I wanted to make a film about the possibility of love to bloom with time," he said. "This film is all about what love is, both for a couple, but also for a family and for a community and for parents and children and for all the different ways in which we love each other, and all the ways in which that is a very complicated act."
Follow AP Entertainment Writer Sandy Cohen at www.twitter.com/APSandy.