Ma’am is an American expression. It’s understood, but sounds overtly American to British ears, like “U wot m8” does the other way around. You wouldn’t hear it at a British drivethru unless there was an American working there.

That said, the artist is British and the car looks like a squished Mk4 Ford Fiesta to me, which didn’t exist in the US but were everywhere in the UK.

So it’s probably a reference or quote of something.

@Brass Melody  
Or just a call about your car’s extended warranty.
 
(Not even running gags are safe.)

@TheDog  
That or that burger shop in Persona 5 saying you won their contest.

@Ardashir
 
Actually, you get a call from a man named Kenshiro who says this.
 
@ZhaoZoharEX
 
It’s from a comic from an artist named valecity.

@TheDog  
After you eat that, do you get a phone call from a cute Japanese girl named Sadako to tell you that you have only seven days left to live?

@TheDog  
Jesus, my arteries are clogged just looking at that.
 
Also, is your avatar from something, the artstyle looks familiar to me.

@fixman88
 
A Spongebob reference. It basically means:
 
“Double triple bossy” means 6, all-beef patties. However, adding a 4x4 (4 beef patties + 4 slices of cheese) it would be 10 patties. Grill them (replicating “burn it”) in mustard. Don’t forget to squash them down with a spatula first before grilling. Also, you’ll need to add butter. But not too much, as “axle grease” means butter and “light” means not too much. Hide the patties under American cheese.
 
Deluxe would mean iceberg lettuce, tomatoes, cheese (ignore this because we already used the cheese when grilling the patties), white onions, ketchup and mustard. Thinly cut all of these. to get two lots of these to cut up.
 
“On a raft” means Texas toast, so cut 48 thick slices of toast (you might need at least 3 loaves of bread) which we will use later. Extra shingles means MORE toast to make. Also, for “shimmy and a squeeze”, you can either butter the toast, spread mayo on it or add special sauce. Or, if you’re that hungry, all three.
 
Now, “animal-style”, add all the condiments you have, more special sauce (if you have any more if you used some on “shimmy and a squeeze”) and add grilled onions and pickles.
 
The last part we need to do is “Make it cry”, which is extra onions. If you haven’t ran out of onions yet, you’re done. But you still need to make the actual burger.
 
By now, re-reading it, I’m assuming you’re saying “But Capprio! You forgot to add in ‘Let it swim’!”. Well, “Let it swim” isn’t important. It means to go, and I’m assuming you’re making this at home. So just ignore that.
 
 
And here’s a picture of what such a sandwhich would really look like.
 

@northern haste  
Ok, that was glorious.  
‘Animal Style’ I recognize from In-N-Out’s secret menu but I have no idea about the rest.

Glimmy looks less like she’s trying to decide what to order and more like she’s iring the thicc curves of the intercom.

@SinnerWhoKeepsTrying1978  
I don’t think they are actually placing that order. However, the way they take so long feels like they’re ordering one of everything by name.

@Th3M4nW1thN0N4m3  
In that case, wouldn’t it be easier just to say, “Yes, I’d like one of everything please?”