At the end of the movie, Sleeping Beauty starts to resemble Ms David, while the prince looks like Mr Loechler.
Then the prince pops out a box with an engagement ring in it.
As the film pauses, Mr Loechler takes a ring and turns to his girlfriend.
"I love you with my whole heart, including all of its ventricals, atriums, valves," he says, pausing to explain to the audience that "she's a cardiologist."
He then asks her, "Sthuthi David, MD, will you live happily ever after with me?"
As she said yes, the crowd cheered and the movie song Once Upon A Dream started to play.
Mr Loechler said it took him six months to rework Sleeping Beauty for the proposal.
He also filled the cinema with a mix of friends, family, and seat warmers he found on Reddit.
In sharing the video on Instagram, Loechler wrote, "The only thing better than seeing the smartest person I know completely dumbfounded was knowing we'd get to live happily ever after together."
The video, which has been viewed 5 million times in YouTube, has made many social media users raise their expectations for any future proposals.
