What the cartoon shows
Our character takes one salted bite and unlocks an absurd superhero form. That transformation is the joke, not a nutrition claim.
What the source actually says
A small crossover study gave 15 resistance-trained men watermelon juice concentrate or placebo for seven days before exercise testing. The researchers did not find an advantage for force or bench-press performance in the watermelon condition.
Where the evidence stops
The study tested concentrate, not a slice of watermelon with salt. It cannot prove what every watermelon recipe does, nor can it measure a cartoon-style change in muscle size. The safe conclusion is narrower: this is not evidence for a one-week muscle-building shortcut.
The useful takeaway
Enjoy watermelon if you like it. For real strength gains, look to sustained training and an overall eating pattern rather than a viral food combination.