Daggerfall, that should read. Stupid vCode.
As DougC said, the backgrounds are usually 2D textures. If you manage to get close to them I imagine it would be like walking up to the screen at the cinema. What’s 2D and what’s 3D is often quite easy to spot, as the houses/trees/mountains making up the background look very flat, even from a normal gaming distance. Earlier games often used skies as background. I don’t know of any game where you can get close to far-away background textures. You can reach close background ‘textures’ in many games, like a street adjacent to a street on the inside of the game world, and these areas are usually done in 3D and you can explore.
If you’re really interested in seeing what’s “outside the game world” you should get the original Deus Ex game. It’s a dated game, but still one of the best action games ever released. In this game there are items you can use to upgrade your character. If you choose super-strength and super-jump you can places crates on top of each other, jump on top of the crates, then jump over walls and other boundaries. When you get to the other side you’ll see that the game world (cities) seems to be placed on a big rock floating through space. It’s quite spectacular. Often, you can walk along the wall on the outside, observing unfinshed buildings, finding forgotten items and, on one or two occasions, even a left behind enemy. You can do this in nearly every outdoor level in this game, as opposed to just a few places as with most games.
In one of the levels on Duke Nukem 3D if you turn on the no clipping and fly around with your jetpack, you can get into a crevass that has a message scrawled into the wall.
This is one of my favorite things to do with video games, once I’ve completed them. (It tends to spoil the illusion and ruin the fun of actually playing the game if you go noclip-ping around. You tend to lose respect for puzzles and obstacles in the game.)
Almost all PC games nowadays have the ‘noclip’ and ‘fly’ cheats mentioned above. In “Half Life: Opposing Force”, you could fly up into one of the buildings that was meant to be a ‘facade’ only (as they’re known in the movie industry) and meet the “man in black”.
I also saw a video of “Half Life done quick” where the guy had figured out how to stack the Claymore mines, and climb up them to get to inaccessible parts of the map. With this technique he was able to “walk on top of the world” and complete the game much more quickly. As mentioned in previous posts, often the rendering engine wasn’t quite designed to deal with these “out of band” cases and you’ll get weird effects. I’ve seen some games where you’re supposed to fall into a “bottomless pit” at some point, but if you go in with god + fly, you find the depth is only actually about 15 feet (in game scale) and you can happily stand on the bottom !
Another fun one to play with was the “bomber” scene in “Call of Duty: Allied Assault”. The script has you trapped inside a bomber, flying at altitude, but with ‘noclip’ you can walk outside and look around, in the sky. In that same game, if you “bust out” of one of the scripted vehicle chase scenes, you’ll find that the vehicle happily takes off into the distance without you, but you can still “remotely” control the mounted gun, and fire it.
I know, I know - “Call of Duty : United Offensive.” :smack:
World of Warcraft had a couple of fun ones.
Sometimes, like in EQ, you would fall through the ground and just plummet helplessly for an indefinite amount of time. There was (might still be) a bug in the game where you would then ‘drown’, and if you tried to recover your body, your ghost would ‘drown’ as well! :eek:
In World of Warcraft, there were ‘instanced dungeons’. Basically if you go in there, you get your own dungeon to run through, without any non-party/raid members around. This is a separate zone and you can tell where the entrance is by a whirling portal. Normally you ‘teleport’ to the instance zone, but when the game lags, sometimes you can walk clear through the thing and wander around the other side! (as it turns out, it is identical to the instance, albeit wtihout mobs).
In Planetside aircraft would get very buggy if you landed on uneven ground. Sometimes if a VTOL was parked on a very slight grade, it would start sliding like it was on ice, and plunge right underwater. Normally going in the water destroys vehicles like aircraft, but sometimes if you were still ‘parked’ the game wouldn’t recognize it being underwater, and you’d have your own little submarine. Another amusing thing was a clipping bug that could send aircraft underground. A flying troop carrier was trying to evade several aircraft once, veered into a mountain and went clear through the ground (one of the attackers crashed trying to chase him 
). It was then completely underneath the ground, and when it reached the enemy base crashed into the underground rooms which were totally visible, depositing the troops smack in the middle of the heart of the base.
I was just playing X-Wing Alliance last night. During the final mission of the game, when escaping the exploding Death Star II, I took a wrong turn and ended up in a dark place that I couldn’t escape from. Evetually the explosion killed me.
And during the battle of Endor, if you look hard enough, you’ll notice that some of those many star destroyers don’t actually exist in the game, but are rather painted on the walls.
Yes, they are called “easter eggs”, and several examples have already been given. The quintessential easter egg, believed to be the first ever created, was in the old console game Atari Adventure. You had to find a secret, invisible “dot” which you then carry to a room where the wall, normally impassable, begins blinking. Beyond the wall is a secret room with the game designer’s signature. Here’s a page with directions how to get there (German only, but it’s got pictures.)
Sometimes. In DOOM, for example, if you use the walk-thru-walls cheat code, you can crash the game by viewing too many objects at once, more than what the game was designed for. Normally though, the only real danger is getting your character stuck, or dying in some hideously spectactular fashion. 
In True Crime: Streets of LA, we were constantly trying to get onto the UCLA campus. It’s blocked off by concrete barriers IIRC, but we managed to get the car over it at one point on Royce Drive. We got perma-stuck and had to restart the game.
And so many nasty EQ bugs with the clip! At one point you could stick your face through the wall in Grieg’s End and see into the other room. Also, I’ve many times been sitting against the wall and fooling around with the zoom, only to zoom inside my avatar’s skull. I should take a screenshot. . .
A very old game I played once upon a time was on a B.B.S., and used ANSI graphics to create a 2-D world your little smiley face character could wander about. Some areas were impenatrable (they represented walls, rock faces, etc.), but it was possible to get a teleportation object that allowed you to “jump” anywhere onscreen. On one particular screen, if you jumped to the otherwise inaccessible top left corner, and then took a step (allowable since you were leaving the screen), you found yourself on a boat at sea that was otherwise completely cut off from the rest of the game. A good place to park your character overnight where you couldn’t be mugged by other players.
You all are a bunch of whippersnappers. 
The earliest known recorded instance of “fake distant scenery” is from the atari arcade game Battlezone. The 3D vector landscape had a horizon that included several mountains and an erupting volcano, and arcade legend had it that anyone who could drive (and survive) long enough could actually reach said volcano. They couldn’t, but it sure suckered a number of players.
I remember the SFX chip SNES games had quite a few glitches like this, possibly because they were properly 3D and perhaps the first games produced for a console in such a way. Enough people must have mailed the official Nintendo magazine about this that it was put on their cheat page as if this was something the player was meant to do :dubious:
And, apparantly, if you have a cheat gadget for your N64, you can walk over to a small island in the first level (in the dam’s reservoir) that has a inactive mini-gun and small building. They were supposed to be part of the actual level but were switched off as it were when the developers ran short of time and didn’t bother including the boat ride out to it.
Adding of course after preview ( :smack: ) that the N64 game you could do that in was, of course, Goldeneye.
And now I suppose you’re going to come out and yell at us to stop playing the PSP on your lawn?
The old Nightmare Creatures game for either the N64 or the Playstation had an fun little one—I don’t think I even cheated to get there. In the last level…
[spoiler]You’re battling with a demon/mutant on top the Palace of Westminster as it burns in the great fire of 1834. Over the side of the roof, you can see the rest of the Houses of Parliament burning, quite some distance away.
I somehow either jumped, walked, or got thrown off the roof…and landed in a little courtyard, where little 30ft high “buildings,” including the clock tower, were being consumed by cute little flames, maybe 40 feet away from rooftop where I was supposed to be fighting.
I think I ended up getting burned to death by the special effect fire, but I always liked that one. 
[/spoiler]
“Return to Castle Wolfenstein” has a neat one, too. In one level, if you use “noclip,” you’ll discover a B-25 bomber, engines running, suspended in space somewhere below the level proper—it’s a set for a cutscene at the end of the level, when your character is being airlifted out. You only see the aircraft from a pan shot, then a closeup reaction shot of your character’s face when he’s onboard, but examining the aircraft with noclip revealed that a fair amount of detail went into building it. There’s a cockpit with a legible panel and controls; seats; bulkheads, and even gunports and a rear turret with WORKING machine guns. Double
There still is, and it’s supposedly not a bug. Blizzard has stated that they implemented this because in beta, when fatigue didn’t affect your ghost, people were crossing the oceans by leapfrogging their corpses. For some reason, this was deemed unacceptable and fixed by making fatigue affect ghosts.
SSX Tricky had certain places where the walls weren’t quite tight and if you went off a jump or ran into a building exactly right you’d get off the track. Game physics worked perfectly, though, and you started falling faster and faster until you hit terminal velocity. Eventually, you hit the bottom of the space the track sits in and get “reset” somewhere on the track, just like if you had normally gone out-of-bounds.
Fun moment-
I was a playtester for a really bad monster truck game for the PS2. Every day I’d come in, get the list of bugs, and try to duplicate them, then mark if they were fixed or not, and get screenshots to bring to the programmers.
Anyway, a week before gold, I’m told to just go around and find if there’s anything that’s broken with the new speed-boost charms on the map. I find one pretty quickly (Speed boost, go up the ramp, explode for no reason). The rest of the day I’m doing all the different maps.
My immediate supervisor comes into my office as I’m doing the vegas map, where I grab two speed charms and high-tail it towards a ramp, launching myself off a ramp towards the roof of a building. I can never -quite- make it. It’s close, though.
My supervisor holds his breath, and realizes I can’t quite make it. He sighs in relief, “You know, if you -could- make that, I’d have to kill you, hide the body, and fake the reports.”
Playing some forgotten PC racing game on a friend’s computer, we were astonished when, after zooming up a particular incline, we found ourselves floating - about a mile up, it seemed.
Took several minutes to fall back to the ground.
I guess this is headed towards Cafe Society, interesting thread that it is.
I read an interview with the HL 2 designers. One odd thing about that game is that there are no cut scenes; everything is interactive. They said they had trouble making sure during the semi-scripted parts that the player couldn’t “bust out” of the script.