Marvel's Incredible Hulk is typically presented as a loner, but that doesn't mean Bruce Banner hasn't had his share of romantic interests throughout the decades. The most well-known partner of Banner's is Betty Ross, the father of which is General "Thunderbolt" Ross, a classic Hulk enemy and frequent presence in the Marvel Cinematic Universe. But one of Hulk's romantic partners, Marlo Chandler, was drastically rewritten to appease Marvel editorial.
Before one can understand Marlo Chandler, one must first understand the nature of Bruce's powers. Banner and the Hulk are treated as separate entities - while they occasionally share memories, they act as different personalities. The most well-known personality is the "savage Hulk": a green-skinned and quick to anger brute with the emotional maturity of a child. The Savage Hulk wants to be left alone more than anything else. A second personality is that of Joe Fixit, a gray-skinned ego-driven Hulk who dresses up in expensive suits and has a taste for the finer things in life. He doesn't have Banner's genius-level intelligence when it comes to science, but can at least speak and present as a human (albeit a shockingly tall and large one).
Marlo Chandler was first introduced to Joe Fixit by reputation in The Incredible Hulk #347 as the Mystery Man of Las Vegas and the city's most eligible bachelor ("From what I've heard, he's incredible!"). In the issue, Marlo is shocked by Joe Fixit's appearance at first, but quickly warms up to him. Marlo would eventually go on to meet Bruce Banner (who introduces himself as Joe's brother, no less), and eventually find out the truth that links Banner, Mr. Fixit, and the Hulk. Marlo was written as an aerobics instructor, but that wasn't always the writer's plan.
Longtime Hulk writer Peter David, who wrote for the character for over ten years, revealed that he had an entire different profession in mind for Marlo:
"Originally, Marlo was supposed to be a call girl. And since she was to be Joe Fixit’s date, she was a biiiiiiig call girl. And her room mate was also a call girl. Then at the last minute I was told I couldn’t have Joe Fixit dating a call girl, so I changed her to an aerobics instructor and her room mate became a nurse. Why, I’ve no clue."
One can infer David's original intentions with the artwork and dialogue choices showing Marlo's debut. The late 80s were indeed a time of pushing the envelope, but it wouldn't be until the 90s and the Dark Age of Comics when such professions were permissible in comics.
In the Marvel Cinematic Universe, Bruce Banner lacks a love interest of any kind. Betty Ross hasn't been seen since 2008's The Incredible Hulk (outside of a Marvel's What If...? episode), and Bruce and Natasha Romanova's short-lived flirtation only lasted until the end of Avengers: Age of Ultron. It's entirely possible that Marlo Chandler could return in a future Hulk outing - but perhaps not with Peter David's original plan for the character.
Source: CBR.com