Anyone else's baby get chunky suddenly?

br

I feel like my son will randomly get chunky out of nowhere and then slim back down...

Here's a picture from last Friday

And Monday

And now Wednesday night

He's always had chunky legs, but he's noticably got chunky in the face over the last few days. Does this happen to anyone else? It's happened a few times in the past as well and then he thinned out again.