Okay, so everybody poops. And we all eat, breathe, fart (except women, according my mother), burp, blink, scratch, etc. But how do you integrate the facts of life with a character who does not, technically, need to eat or use the restroom?

Eating
Just like any scene in your novel, we only need to see the character eating when it’s important, or when what they’re eating sets the scene. For example, if Hallie is inviting her crush over for dinner, what they’re eating helps to set the scene. Consider:

Hallie stirred the marinara sauce and set it to simmer. She quickly diced an onion and threw a handful into the mixing bowl with the ground beef and breadcrumbs. Her mother wasn’t the only chef in the house.

She’d watched her mother seduce many a boyfriend with a meatball and a glass of wine. Obviously, wine was not in the cards for her and Connor. And it’s a bit difficult to seduce anybody when your mom is sitting at the table with you. But Hallie was confident in her cooking. And she also knew her mom had to leave for the restaurant at eight.

Versus:

Hallie took one look at the package of ground beef and almost vomited.

“How do people do this?” she asked the otherwise empty kitchen.

She grabbed her mother’s dish gloves, jammed her hands into them and picked up the pound of beef. Gloves still on, she tried to peel the onion, but settled for a generous sprinkle of onion powder instead. After measuring the basil, garlic powder and salt, Hallie stuck her gloved hands into the mix.

“Connor better freaking appreciate this. I don’t even likemeatballs.” She squeezed the meat between her rubber yellow fingers.

Half an hour later, something was starting to burn…

In both scenes, we know they’re eating meatballs, but the description in the first scene gives the impression that the meal is going to be a romantic, successful affair. The second scene sets us up for quite a different night.

Breathing
Sometimes manuscripts can be quite “breathy.”

Everyone is always “heaving a sigh,” or hyperventilating with “short, quick breaths.” A character’s breathing pattern can help give the reader a sense of their emotional state. But be careful not to use this as the only clue. In the list of cliched body movements, certain breathing patterns are high on the list.

Pooping
In general, a character should be in the bathroom because the plot action requires them to be there. The reader assumes the character is, um, regular — if they give any thought to bathroom habits at all. So unless it’s absolutely necessary to drive the plot forward, let’s keep the bathroom door closed, shall we?

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More on Character:

Spotting Character Contradictions

Who Is Your Protagonist’s Daemon?

Great Posts on Character and Dialogue