Since at least July 2017, rumors that McDonald's was once sued by a man who was still depressed after eating a Happy Meal have resurfaced periodically:
This story was first published by 8shit.net, which — true to its name — only publishes satire and hoaxes:
Some people take marketing campaigns very seriously. This is the case of Ruben Caradehuevo, a depressed man that sued McDonalds for about $1.5 million dollars because after he ate his happy meal, he was still depressed.
[...]
"I bought my happy meal, thinking that that would be the perfect solution for my depression", Caradehuevo relates. He kept going: "I started eating and I was half way done, but my depression was still there", he states. After finishing his food, the depression hadn’t still gone away, and he got really pissed.
A disclaimer in the footage of the web site states:
8Shit is a satire news and humor website. All its content is fiction (except those posts under the “serious” category) and shouldn’t be taken as real. All references, names and marks or institutions in this website are used as contextual elements, like in any novel or science-fiction story.
This fake news stories may invoke memories of another "frivolous" lawsuit against McDonald's from the 1990s when the company was sued for serving coffee that was too hot. Although that lawsuit was real, it was not as frivolous as it is often presented.