someone's faxing me a snickers

Dropping the kids at the pool.

In our language "sitting" is a synonym of "meeting". So in the office setting, I always say "I have an important sitting coming up".

Honk out a dirt snake

"Gotta use the sandbox"

Lay a sewer pickle

"I gotta go do some paper work" or "I need to get something down on paper" are my two go-tos

I've got shit to do

"I need to poo-poo in the pot-tay"

"I'm sitting on a cigar"

I need to go 3D print something.

i say “gotta go log out”

i do freelance work with technology, and the clients think i am going to do something work related and technical.

I gotta drop the Browns off at the Superbowl.

I'm gonna try and lose some weight

Gotta make a deposit at the porcelain ATM.

Gotta paint the town brown

Gotta curl one out

Gotta pinch a loaf

I'm gonna run for the White House

The chocolate bus honks.

My favorite is, "boss makes a dollar, I make a dime. I'll be back in awhile."

Gotta make room for dinner

Touching cotton, gotta go.

Turtle's poking its head out.

Farting freckles.

Making fuzzy rope

"All hands rig for dive. DIVE DIVE DIVE"

And my absolute favorite to use in the office or around older family / the youngins, "I gotta go make"

"Gotta see a man about a dog."

Had a coworker that would go the the bathroom and sit in there for 10 to 15 so I started calling it a "Tony ten-er."

I find myself quoting a line from Farscape a lot:

Must...Excrete...

I'm gonna go drop the kids off at the pool

A silly Dutch one is saying you got a fax from Darmstad, which is a city in Germany but also Darm=intestines and Stad=city.

In Dutch or Flemish at least we say: Ik moet een grote boodschap doen.

Which is a literal translation for: I have to make a big message.

Not exactly an answer to your question but hey what a coincidence

Taking the Browns to the Super Bowl

(the cleveland browns are an american football team)

"I'll be right back, gotta check if the bathroom still works"

"Gotta go read The Hobbit" after my dad claimed he could do it in one 'sitting'.

I need to pinch a loaf.

Gotta drop the kids off at the pool

Gotta work my shift at the fudge factory.

Gotta send teal'c through the stargate.

I quote cars.

There's a rumble in the Bronx

There's big trouble in little China

The spice must flow

Time to go take the Browns to the Super Bowl.

If I have to pee I'll say "I have to pee" if I have to shit I say "I have to go to the bathroom"

I need to practice the tuba.