On Mardi Gras morning, my proposed costume sparks a debate. To correspond to daughter Sophie’s depiction of “Harry Potter” heroine Hermione Granger, I’ve settled on another character from the series: Severus Snape, the grim, black-clad potions instructor.

But Snape, I insist, would not go to Mardi Gras as himself. He would morph into a woman.

The necessary props are at hand: The black wig I wore to serenade my wife as Journey’s Steve Perry at Rock ’n’ Bowl. Tights and a long-sleeve, form-fitting black dress, of indeterminate origin, from the house costume bag. A pair of riding boots, borrowed from my wife. A hooded black cape, from an old Mexican wrestler ensemble.

And two plush, Endymion 50th anniversary footballs, caught the previous weekend, to provide appropriately eye-catching cleavage.

Somehow, I often end up in drag on Mardi Gras. It’s something of a family tradition. Forty years ago, my hirsute father joined other dads to perform as hula dancers at the Lutheran grade school his sons attended. They slayed.

But my Carnival cross-dressing is vetoed. Yielding to pressure, I agree to be a straight Snape, sans cleavage. The dress, tights, boots, cape and wig will have to suffice.

Sophie, at 8, is still borderline mortified. “You look ridiculous, Dad.”

To the contrary, I don’t think I look ridiculous enough. What’s the point of a license to be absurd if you don’t fully embrace it?

The Carnival season had already yielded its share of moments. On Magazine Street one night, I hoisted Sophie and her friend Zoe up a street sign’s pole. “Isn’t it our job to keep them off the pole?” Zoe’s dad observed.

Sam, nearly 6, started wishing people “Happy Mardi Gras” shortly after Halloween, his other favorite holiday. Content to wave at floats from a distance, he nonetheless secured an awesome plastic shield and battle-ax.

In related news, his little sister Celia now sports a small cut on her nose.

Sam and I were projected onto Endymion’s E-TV video-wall float as it rolled along Orleans Avenue. At the same house party, we briefly, and scarily, lost Celia before she was discovered happily bouncing among older kids on a backyard trampoline.

If Mardi Gras morning temperatures are below 50 degrees, my wife stays home with Sam and Celia. Thus, for the second consecutive year, Sophie and I — aka Hermione and Snape — are on our own.

We park downtown off Poydras Street. The goal is to rendezvous with friends at St. Charles Avenue and Foucher Street — a hike of nearly 3 miles, each way. No problem. My (wife’s) boots are made for walking.

Pete Fountain has already passed by, but Zulu is still rolling. “Zulu is mostly Native Americans?” Sophie asks.

It may be time for her to brush up on the Carnival basics.

The stroll along the St. Charles Avenue parade route bisects the strata of New Orleans society. At every level, Hermione is a hit. A buxom lady in a green flowered dress takes a picture with her. A 20-something woman, drink ? — not her first — in hand, coos, “Hermione is my hero.”

Sophie beams at every acknowledgment. “I didn’t think so many people knew about Harry Potter!”

Snape’s recurring wardrobe malfunction requires frequent adjustments. “I’ve got to pull up my tights,” I announce.

An eavesdropping woman says to Sophie, “You will never hear that line again from your dad.”

Sophie sighs: “I’ve heard it a lot today.”

Zulu gives way to Rex. The king of Carnival glides by aboard his royal float. Hermione’s hands and face are coated with blue cotton candy residue. His majesty, waving in the opposite direction, does not notice.

All of Rex passes before we arrive at our destination. After the first two dozen semis of the subsequent truck parade, it’s time to reverse course. At Fourth Street, I realize my cloak is missing. Backtracking to Eighth, we discover a sad little pile of black fabric lying by the curb — a Mardi Gras miracle.

On the opposite side of St. Charles, the procession of consecutive parades has halted. Far ahead, Rex is saluting his queen.

We press on. Sophie steps on 730 pieces of trash before she stops counting. In the crowd at the corner of Felicity, a cop swats away a drifting cloud of pot smoke. Extra vigilance is required along lower St. Charles, where ugly reality sometimes intrudes on Carnival fantasy. (Alas, two hours later, there is a shooting; thankfully, nobody dies.)

We catch up to the last third of Rex. On the back side of Lee Circle — or Me Circle, as Krewe d’Etat rechristened it in “tribute” to a certain monument-removing mayor — we tuck into a lightly populated pocket between the stands and barricades. Hermione on Snape’s shoulders proves to be an effective lure for throws. Excess necklaces are stashed in my boots, alongside Hermione’s wand.

Sustenance is needed. At the downtown Company Burger, the bathrooms are clean and there’s no line at the counter. Cheeseburgers, fries, onion rings and shakes make for a late-afternoon father-daughter Fat Tuesday feast. A smattering of Zulu riders, still in their costumes and fake Afros — but clearly not Native Americans — are similarly inclined.

Outside, a lone man in a kilt strolls Poydras Avenue, away from the action. The lonely peals of his bagpipe are soon drowned out by a police car’s siren.

That signals the end of our Mardi Gras. There’s nothing an 8-year-old needs to see at sunset in the French Quarter.

At home, we consult the Rex parade bulletin from that morning’s newspaper; we caught customized necklaces from the final eight floats. It was a successful outing, for multiple reasons.

Earlier, Sophie marveled at the combined length of Zulu, Rex and the truck parades: “It seems like this parade goes around the whole world.”

The whole world should be so lucky.

Staff writer Keith Spera chronicles his parenting adventures in the occasional ‘Parental Advisory’ column.