What does "topple over" here mean?

[v0031]

Rolex, a 5-month-old puppy, is making the Internet fall in love with him, thanks to his adorable viral video, in which he's seen eating the fruit while sitting inside it. At one point, little Rolex and his watermelon topple over.
It's not the only human food Rolex enjoys, his owner, Natalie Shalom, told ABC News.
"He also loves peanut butter," she said.

[True Federalist (진정한 연방 주의자)]

Topple is a synonym of collapse or fall. To topple over, collapse over, or fall over is to fall in a fashion that where you land is not directly below where the subject of the verb was standing but off to one side.