Secrets and Easter Eggs in GTA IV

The following is a list of secrets, easter eggs, and hidden trivia references in Grand Theft Auto IV.

Easter Eggs

 * Inside the Statue of Happiness is a giant beating heart. This is supposedly the "Heart of Liberty City."
 * Whilst on a mission with Packie, if you position the camera properly you can look inside his head - inside there is a box with a picture of a brain on it.
 * While driving the Mr. Tasty, you can trigger songs to play by clicking the horn. One of these songs is the song from the opening credits of GTA4.  While this song is playing, call ZiT and they will text you back with "GTA4 theme song found".  This is a cheat that gives the player health, armor and ammo, but also disables some achievements.

References to previous games

 * Descending down the stairs of your first apartment in Hove Beach, you may spot some graffiti referring to past GTA protagonists Claude, Tommy, Carl (CJ), and Toni, and Victor.
 * There is a Sprunk manufacturing plant in Alderney. Sprunk was featured in GTA Vice City, GTA San Andreas, and Manhunt. It has returned to GTA IV with a brand new look. Also notice that "Sprunk" is a mix of the words "Sprite" and "Spunk".  The sign outside the factory is very similar to a sign for Pepsi-Cola that appears in the film "The Great Gatsby."
 * One of the TV shows is a program called Las Venturas Poker. It features a casino from GTA San Andreas.
 * In Star Junction there is sign for Love Fist. Love Fist was featured in GTA Vice City, and was also on a sign in GTA San Andreas.
 * In the apartment in Bohan, next to the coffee table and in front of the bed, are a few CDs laying on the floor. Zoom in with a sniper to see that one of the CDs is by OG Loc from GTA San Andreas.There is also one of Madd dogg
 * There is a laundromat in Alderney called Mr. Wong's Laundromat; this is the same one from GTA III.
 * When you kill Playboy X, go to his apartment to get clothes that that look like the clothing of Claude, the protagonist of GTA III.
 * On the front of the Liberty Tree is Donald Love, who disappeared in GTA III.
 * The Securicars have the words Gruppe 6 on them, a reference to the Securicars in GTA III and GTA Vice City, which had the words Gruppe Sechs (group sex) on them. The initials would be G6, which in German are pronounced (gay-sex).
 * In the bars are postcards featuring Vice City. Vice City is also advertised in airfare billboards near the airport.
 * The "Pager" ringtone on Niko's phone is music from Vice City.
 * Niko can receive an email from Chiliad8888, which calls the recipient "Pilgrim", makes many spiritually- and philosophically-charged (and anti-government) comments, ends with "Feel the Truth, Live the Freedom", and links to whattheydonotwantyoutoknow.com. On this website there is a discussion topic titled, "Jump to a new level of Spirituality" posted by "Trooth".  This discussion thread includes more philosophical thoughts, mentions peyote, and provides a map of the Unique Stunt Jumps in Liberty City.  These clues all suggest that the author of the email as well as the discussion topic is The Truth, a character from GTA San Andreas.
 * On Happiness Island, infront of the entrance to the statue, it is possible to find an artists tripod with several pictures on. These pictures are all concept works of many previous GTA characters.

References to other games

 * One of Rockstar's rivals, THQ's Saint's Row, has been parodied on various billboards and signs throughout the city as a seafood restaurant called "Squid Row - Budget Seafood."
 * In the amusement park in Broker there are blue/purple Hippo Statues, just like the ones from Manhunt.

Real-world references

 * Rockstar Games has a habit of putting its logo in its games; the bowling pins at the bowling alley have the Rockstar logo on them.
 * In Cluckin' Bell restaurants, near the back of the store, there's an action figure of a man in a martial arts position wearing a chicken hat; printed on the glass is "Cluck Norris," which is a parody of television star Chuck Norris, an expert in martial arts and the inventor of his own martial art and the roundhouse kick.
 * The mission Weekend at Florian's is a reference to the comedy movie Weekend at Bernie's (Florian insists that his new name is Bernie).
 * The mission called I Need Your Clothes, Your Boots and Your Motorcycle is a reference to Terminator 2: Judgment Day, in which Arnold Schwarzenegger says this famous line.
 * Many street names in Bohan are named after prisons.
 * Leavenworth Ave, Alcatraz Ave, Sing Sing Ave, Guantanamo Ave, Attica Ave, San Quentin Ave, Folsom Way (best known from "Folsom Prison Blues" by Johnny Cash), Rykers Ave (Is named after a prison that sits in the East River between Queens and the mainland Bronx, adjacent to the runways of LaGuardia Airport called rikers island in New York), Joliet Street
 * Streets running east-to-west (horizontally) in Algonquin are named alphabetically after different types of minerals. "A" is at the southern end of Algonquin; "X"  at the northern end.
 * Amethyst, Barium, Calcium, Diamond, Emerald, Feldspar, Garnet, Hematite, Iron, Jade, Kunzite, Lorimar, Manganese, Nickel, Obsidian, Pyrite, Quartz, Ruby, Silicon, Topaz, Uranium, Vauxite, Wardite, Xenotime
 * On the Algonquin Bridge from Algonquin to Broker, on the right is a building with the name "CLOCKTOWER"; this is the reminiscent of the "WATCHTOWER" building of the Society of the Jehovah's Witnesses in Brooklyn.
 * At the beginning of Clean Getaway, Vlad is nearly hit by a taxi and shouts "Hey! I'm walking here!" in reference to Midnight Cowboy.
 * In the South of Alderney the street names reflect military troops, "Muskteer, Grenadier, Chariot, Phalanx etc".
 * In Broker roads running North-South are named after native american tribes, " Iroquois, Oneida, Mohawk, Onondaga etc".
 * In south Dukes and north Broker there are the street names "Cassidy" and "Sundance", a referance to the film Butch Cassidy and the Sundance Kid.
 * Broker contains the streets "Ringo St" and "Starr St", a referance to the Beatles member Ringo Starr.
 * Rockstar uses cartoon characters names as street names sutch as, "Bart (simpson), (Hubert) Farnsworth" and the direct link th South Park, "South Parkway".
 * Some streets are named after tools, "Jackhammer, Plumbbob, Tinderbox".
 * Some streets are named after animals, "caterpillar, Worm, Butterfly".
 * Some streets are named after foodes, "Onion, Asparagus, Chive".
 * Some streets are named after colonial Settlements, "Yorktown, Delaware".
 * Some streets are named after celebrity surnames, "Harrison, Hancock" also some explorers, "livingstone".
 * Some streets are named after nuclear tests, "Plumbbob, Emery, and Niblick".
 * On the stairway leading to the sea at Meadow Hills there is a 'banksy-esque' style graffiti piece.

Adult humor

 * The outside sign for the Memory Lanes bowling alley depicts a bowling pin with two bowling balls on either side of it. Inside, however, the sign is only a neon outline, and resembles a crude drawing of male sex organs.
 * In many spots around Liberty City, there is rubble on the ground; in some of this rubble, you can see a purple dildo sticking out.
 * There are signs scattered throughout Liberty City that say 'Hot Coffee Shop,' clearly a reference to the Hot Coffee sexual content and controversy from GTA San Andreas
 * Looking at the golf courses carefully from a height reveals that they are penis shaped.
 * A brand of beer in the game is called 'Dusche Gold.' "Dusche" is German for "shower", so it translates into "Shower of Gold."
 * The Statue of Happiness's name, when said fast is "Statue of a Penis."