"You mean Hagrid? He works at Hogwarts. He's awesome; he's helping me get my school supplies." It's kind of cool knowing something Hogwarts-related that the kid raised with magic didn't. Also it's rude to visibly freak out over how tall people are. Bruce was freaked out by Hagrid at first too but in his opinion it doesn't count as rude if the other person just kicked your door in.

"Ohh, right, yeah, I've heard about him," Draco relaxes immediately. Nothing is scary so long as you have a cached mockery script for it on hand, right? Right.

"He's a sort of savage or something - lives in a hut in the school grounds and every now and then he gets drunk, tries to do magic and ends up setting fire to his bed." 

Wow, what. "Do wizards actually call people savages? Anyway, he hasn't"--he remembers at the last second that Hagrid's ability to do magic is a secret--"done anything silly that I've seen. He's cool." Alright, giving Dudley a pig's tail was pretty silly, but still.

"What else would we call - oh, there's Father," grins Draco, thoughts of racing broomsticks promptly overwhelming any uninteresting discussion about racist nomenclature, and he exits the conversation at speed without a single look back.

"Mornin'!" booms Hagrid, failing to detect Draco scurrying away below his plane of view and sticking his enormous fuzzy head through the door to grin at Madam Malkin.

She looks up from her chart of inscrutable numbers and waves. "Hello! Hogwarts business, Hagrid?"

When Hagrid's chest puffs up proudly it causes him to bonk his head slightly on the doorframe. "Oof - yes! Taking young Mr. Potter to get all his things, o'course. Doin' all right, Bruce?"

"Yes mister Hagrid." Did the measuring tapes finish up with him yet? Is there anything else he's supposed to be doing right now?

The measuring tapes are now buzzing about in a cloud around Madam Malkin, and she is humming to herself and making notes, glancing in his direction occasionally. This probably means they're done?

There is, perhaps, a certain discomfiting ambient sense that Bruce is supposed to have figured out by himself whether he's supposed to do anything else, using the approximately zero (0) information available to him on the social cues channel.

The other kid didn't get any robes before he left; maybe they deliver? Does he need to tell someone his address? He didn't for the letters but that was a more complicated situation. 

"Uh, ma'am? Do I need to do anything else? Sorry, I've never done this before."

Madam Malkin looks up. "Oh! My apologies, dearie. You're quite done, the rest is your - ah -"

(she shuts her mouth very firmly around the shape of the phrase your parents)

" - Hagrid, will he be taking delivery now or by owl?"

"Hrm." Hagrid's face disappears out of the doorway for a moment as he straightens to his full height to stare contemplatively into the middle distance, considering with some dismay the prospect of the Dursleys receiving a package by owl delivery. Then he leans back down - he has to bend almost double at the waist to fit his head in the door - and says firmly, "ah, today. Time fer lunch while we wait, yeh think?"

Madam Malkin considers the small child before her, and her chart of numbers informing her firmly of his dire need for nutrition, and says, very enthusiastically, "oh, yes, you go right ahead, my dear. Come back in an hour."

"Okay, thank you!" Time to go find out what wizards eat for lunch!

If you are Hagrid, for lunch at the Leaky Cauldron you eat an entire casserole dish sized pot pie and drink a mug of beer the size of a lesser man's head. Bruce, on the other hand, is presented cheerfully with a reasonably normal-sized bowl of soup.

Apparently, it is the Leaky House Soup. Not to be confused with the House Leaky Soup, the House House Soup, the Leaky Soup House, et cetera.

As long as it goes from the bowl to his face without attempting to go anywhere else, it's good! He'll pay for his out of his school supply money unless Hagrid pays for both of them.

Can they get textbooks next after they pick up the robes?

Hagrid seems to have already paid.

He blinks a little bemusedly at this request - most eleven-year-olds are not excited about textbooks - and then, all at once, grins so broadly and warmly that it's tempting to consider the possibility that he may be literally glowing. "Ahh, just like yer mum."

Bruce grins back. Food and magic textbooks and responding well to being asked for something and acknowledging the existence of Bruce's mother? Truly Hagrid is the best adult and anyone who thinks otherwise is a fool.

What a delightful small child. Hagrid absolutely cannot fathom how the Dursleys could manage to be Like That at him and live with themselves.

When they're done eating, he leads the way to Flourish & Blotts, which is an enormous wooden building whose door is actually large enough for Hagrid, though he has to squeeze his way somewhat carefully between several precariously stacked piles of the newest edition of Quidditch Through the Ages that are crowding the entranceway. "Here we are!" Hagrid says brightly, gesturing proudly about and narrowly avoiding smacking a fluttering Broom Maintenance Charms For The Quidditch Professional out of the air with his elbow. "I'm not much of a books person me'self, but I never needed one I couldn't find here or in the library."

Magic bookstore magic bookstore he's in a magic bookstore and he has money!

He will grab all of the textbooks on the list and three more books on magical theory and two on astronomy and another one by the author of One Thousand Magical Herbs and Fungi and one on alchemy and why shouldn't he just get what looks like next year's transfiguration book now, and ohhhhhhh wow does "arithmancy" mean there's magic math, yes it does and now his pile of books is taller than he is and he needs to push it over to a corner and do some normal math about how many of these he can fit in his budget and his trunk. But first he needs to climb this shelf just a bit so he can get Principles of Spell Development. (He falls off, but he gets the book and doesn't bring anything else down with him, mission accomplished.)

Bruce will learn, then, that the shelves in this bookstore (which has had about four hundred years to optimize for regular influxes of excited eleven-year-olds) are enchanted so that if you fall off of them you fall down very slowly and gently.

Hagrid peers at the stack of books. He was emotionally prepared to have to gently discourage the purchase of the sort of thing James would have wanted when he was eleven and immediately injured himself with, but Bruce doesn't seem interested in curses. Extracurricular facts about plants and math seem fine. "Think yeh can prob'ly get the astronomy ones in the library?" he suggests, instead, while he's squinting suspiciously at the alchemy book. Hagrid does not really know enough about alchemy to be confident that it is not horribly dangerous, but then, Flamel seems to be experiencing the exact opposite of dying at eleven from unwise magical experimentation, doesn't he, so... it's probably fine...? 

Bruce is not at this time particularly constrainted by budget, but Hagrid will also remind him that he's got to fit robes and potions supplies into his trunk, and helpfully gesture the approximate dimensions of a standard-sized cauldron. 

What a good feature for shelves to have! He will put back the astronomy books, and also the ones that look like sequels to his current textbooks on the theory that the library might have copies abandoned by yet older students, and the most advanced arithmancy book, and then he can fit the rest and probably still have enough room for robes and potions supplies and his very own telescope.

When Bruce is done pruning, Hagrid will carry the selected books to the counter, since a quantity of books that make up a substantial fraction of Bruce's body weight are an easy handful for him. 

"Oh, Hagrid, hello!" says the manager as they approach. "I hear I owe you a drink? The kids who cleared the booklice out of my second floor last month said they got the idea for the freezing charms from you." 

Hagrid turns a warm shade of magenta. "Oh! Well goodness me, uh, no trouble at all, glad to help," he blusters delightedly. 

This is yet more evidence that Hagrid is the best adult. Bruce loads books into his trunk as they get rung up, except for Magical Theory by Adalbert Waffling which he hangs onto to read first.

"What're booklice like? Are they like bookworms but lice-shaped? Are they magic or just regular bugs?"

Animal facts!! Hagrid loves animal facts. They are his favorite thing. He will answer that question at length on the way to the apothecary.

"Ooh! So see - yeh know how there's a lot of kinds'a dogs? - people'll call all sorts'f stuff bookworms, beetles and lice and even paper salamanders and things. Anything that'll eat a book, that's a bookworm, they'll tell yeh, but heck, a dragon'll eat a book if yeh put one in its face, won't it, I think really it only counts if they'll go hunting for 'em on purpose. Anyway a book louse is a lil tiny bugger," he pinches his thum and forefinger together illustratively, "oh, 'bout a breadcrumb? An' they like ter be warm, see, so, make 'em cold and off they trot, no poison sprays or anythin' that'd damage the books!"

He seems puzzled, though, by the question of whether they are magic.

"....I think most things're at least a bit magic?" he hazards.

"That's a really clever solution! But if every living thing's a bit magic why haven't scientists noticed? Is it just a really tiny bit?" Maybe most magic is like neutrinos and doesn't do anything and wizards and witches and dragons happen when it starts doing stuff.

Why haven't...

"Scien..tists?" repeats Hagrid, a little dubiously. "Those blokes who build the funny contraptions an' blow things up?"