Yell FUCK. For no other reason than its going to happen whether you want it to or not. Remind your older child that it’s an “adults only” word later. Then attempt to take a deep breath while avoiding smelling anything. This is going to get messy.
Remove his clothing. Do this slowly, so the mess doesn’t spread, but quickly because he’s thrashing around like a crocodile that’s just been tackled by Steve Irwin. Then be careful not to brush the soiled clothes up against your clean, white shirt or it will never see the light of day again.
Deal with the diaper. Ok now. This is ground zero: the epicenter of the atomic shit that blew up a diaper, a onesie, and the cutest pair of overalls he owns. It also somehow got on his socks and in his hair but don’t lose focus on the diaper. Grip it firmly, fold it into itself if possible, and dispose of it with two fingers like a bomb disposing robot handling an incendiary device. Get it into a plastic bag if you can. This is it: the reason why you’ve had all those trips to Target: free atomic diaper disposal bags.
Use every wipe in the box. This will assure your baby becomes as clean as he can get in an Applebee’s bathroom. Get the butt, the legs, the arms, his hair, somehow his ear now, his feet, all of it. Don’t forget your own hands and your tears.
Replace his outfit with the backup outfit. It was his sister’s romper from 5 years ago. It has a pink butterfly on it. But if your friends gender shame your baby then they’re bigots so fuck them.
Give the older sibling lots of one-on-one time later. She needs it. This baby is taking away all the attention. Being a mother of two is insanely hard.
Drink wine. Not a glass, the whole bottle. Don’t be a bitch. You’re a good mother, but sometimes you need a mini-vacation inside the bottle of a rich Napa Valley Cabernet.