The McDonald's lawsuit was legitimate. People know coffee is hot and yes, the plaintiff was clumsy enough to spill it on her lap, but people DO NOT expect their coffee to give them THIRD DEGREE BURNS that require skin grafts! That
is over the top kind of dangerous to the point of negligence, not just "ouch that was hot coffee, I'm going to sue McDonalds because I spilled it on my lap and it hurt for a minute." Third degree burns are the 2nd most serious kind, folks. She was in the hospital for a week.
McDonalds was IMO lucky that coffee that hot never spilled on a child.

They would have been sued right into the ground.
90% of "frivolous" lawsuits are justified once you go over the important details.