Charlie and Frank's apartment is a Single Room Occupancy (SRO) apartment. It's dominated by a pullout couch, where Charlie and Frank both hang out and also sleep facing ass to ass according to Frank. ("Who Pooped the Bed?")
To the right of the couch is a stack of records and a guitar, and to the left is the cooking area, home to Charlie's hot plate, mini fridge, and radiator by the dining table. There are also two dressers against the wall opposite to the couch, one of which holds the television.
There are two windows in the apartment, which Charlie sometimes covers during the day. ("Sweet Dee's Dating a Retarded Person")
The apartment is on the 2nd floor of the building. ("Mac's Mom Burns Her House Down")
The apartment number is 210 ("The Great Recession")
There's a large closet that has enough room for a bed, if it's cleaned out. (This might imply that the apartment actually has a separate bedroom that Charlie either doesn't know about or doesn't use, for some reason.)  Charlie states that he has to sleep in the closet when Frank brings home a hooker. ("The Gang Turns Black") There are three other doors in the apartment: one next to the closet which is usually shut, though has a light in it, ("Charlie Has Cancer") one on the same wall near the window which is usually boarded up, and another across the room, the bathroom.
There is what appears to be a small maintenance closet near the entrance that has a dirty mirror and sink, where Frank does his morning routine. ("Being Frank")
The apartment is small and cluttered, so it does not have many good places to hide. Charlie's preferred hiding place is to lie under the sheets of the fold-out bed "like a starfish" ("Mac's Banging the Waitress"). Frank likes to hide inside the sofa itself, where he often catches Charlie "pounding off". ("A Very Sunny Christmas")
Charlie and Frank urinate into open cans of urine that they leave lying around the apartment. Charlie tells Dee that she does not want to use the restroom. ("Dennis Reynolds: An Erotic Life") As of 2016, Hwang has not fixed the plumbing. ("Being Frank") This would agree with the advice Charlie gives to Frank about showering in the bar's sink when he first moves in. ("Charlie Gets Crippled") We learn that there is a "shitter" down the hallway, which does not have a door so Frank and Charlie take turns being the door for each other ("The Gang Gets Romantic").
There are also no heating ducts, so the apartment gets extremely cold at night. As a result, Charlie wears thermal wear in the apartment and also sleeps back to back with Frank. ("Dennis Reynolds: An Erotic Life")
The apartment is surrounded by 50 cats which meow all night long, so every night Charlie eats cat food, huffs glue, and drinks beer to feel sick and tired and fall asleep. ("Dennis Reynolds: An Erotic Life")
Charlie's landlord is named Hwang.("Gun Fever") Charlie, who is always broke, was usually late with his rent payment until Frank moved in. ("Charlie Gets Crippled") According to Hwang in Gun Fever, the rent he's owed is $854, though it's unclear if that's for one month or if it's all the money Charlie owes him.
Charlie's most cherished possession in his apartment is his hot plate. ("Dennis Looks Like a Registered Sex Offender")
There seems to be a bedbug problem in the building: the building has been fumigated at least once for them, making Frank unable to go back into the apartment to get The Gang's World Series tickets ("The World Series Defense"), and later, Dee's face gets inflamed from bedbug bites after she sleeps in the apartment. ("Mac's Mom Burns Her House Down")
Frank keeps several boxes full of pennies stashed in the apartment. ("Mac Fights Gay Marriage")
- Season One: Charlie Has Cancer, Gun Fever, The Gang Finds A Dead Guy
- Season Two: Charlie Gets Crippled, The Gang Goes Jihad, Hundred Dollar Baby, The Gang Runs for Office, Dennis and Dee Get a New Dad
- Season Three: The Gang Finds a Dumpster Baby, The Gang Solves the North Korea Situation, Sweet Dee's Dating a Retarded Person, Mac Is a Serial Killer, Dennis Looks Like a Registered Sex Offender, Bums: Making a Mess All Over the City
- Season Four: Mac and Dennis: Manhunters, The Gang Solves the Gas Crisis, Mac's Banging the Waitress, Mac and Charlie Die (Part 1), Mac and Charlie Die (Part 2), Who Pooped the Bed?, Dennis Reynolds: An Erotic Life, Sweet Dee Has a Heart Attack, The Gang Gets Extreme: Home Makeover Edition
- Season Five: The Great Recession (mentioned only), The Waitress Is Getting Married, The World Series Defense, Paddy's Pub: Home of the Original Kitten Mittens, Mac and Dennis Break Up, A Very Sunny Christmas
- Season Six: Mac Fights Gay Marriage, Mac's Mom Burns Her House Down, Charlie Kelly: King of the Rats
- Season Seven: Frank's Pretty Woman, How Mac Got Fat
- Season Eight: Pop-Pop: The Final Solution, Charlie Rules the World
- Season Nine: Mac and Dennis Buy a Timeshare, Flowers for Charlie
- Season Ten: Frank Retires
- Season Eleven: Frank Falls Out the Window, Being Frank
- Season Twelve: PTSDee, Dennis' Double Life
- Season 13: The Gang Makes Paddy's Great Again, Charlie's Home Alone
The German Shepherd Painting
Back in Season Two, there was a "very special" German shepherd painting:
- "That was basically just set decoration in the second season. Interestingly enough, we actually were the ones that when we got into editing and we were watching the show - all the episodes of Season 2 - that painting stood out to us so much, too much, it was too distracting. We actually said we never want to see that painting again. Take it down. Get rid of it because it's just a shining, white, weird painting in the background of every Charlie's apartment scene", said Rob McElhenney.
But in fact, they did not just "get rid of it" - they moved it to the RCG office, so you can notice it behind Kaitlin Olson in the scripted "BTS-video" for Season Four "A Day in the Life of Kaitlin Olson" at 01:47. [Also, the decorations for Charlie's musical, which are imitate an interior of his apartment, contains an allusion to this painting.]
Later, in the 8th Season premiere, it is revealed that Charlie found this watercolor painting in the Pop-Pop's box along with Nazi memorabilia and decided to keep it (as well as Nazi peaked cap) because he liked it. ("The Gang Finds a Dead Guy") Nevertheless, between the events of Season Two and Season Three, Frank made Charlie to take it down from the wall, because, how he stated, "Its smug aura mocks me". They put it in the box and stashed away somewhere, but at some point Frank just "threw that thing out".
It also been revealed that this shepherd was painted by Adolf Hitler himself but could not be traced to him because Charlie painted on top of the original painting. At the end of the episode when Charlie burned the painting, the layer peeled off and revealed the true artist, Adolf Hitler.
Frank and Cricket both felt that there was something wrong with this painting: Cricks was talking about its "very evil vibes", and Frank even called it an "evil" itself.
- Frank: I want to live like you again, Charlie! I want to be pathetic and desperate and ugly and hopeless!
- Charlie: I am not ugly.
- Frank: This is the change I've been looking for! I want to move in with you!
- Charlie: Are you out of your damn mind, dude? You made me sleep out in the hall! You ignored my cries for help in the middle of the night!
- Frank: I'll pay for your rent for six months.
- Charlie: Twelve.
- Frank: Six.
- Charlie: Ten.
- Frank: Six.
- Charlie: Nine.
- Frank: Six.
- Charlie: Ten.
- Frank: Six.
- Charlie: Twelve.
- Frank: Four.
- Charlie: Six.
- Frank: Deal!
- Charlie: All right, no more sleeping out in the hall, though.
- Frank: I can't promise that.