Game crash
A game crash, also known as a game freeze, is when a video game freezes up and ceases to respond to any input. Crashes typically occur when the game console's connection with the game is interrupted, when its CPU is overwhelmed by how much it has to process (and runs out of space to hold it all), or when it tries to access something that does not exist. Crashes are usually just an inconvenience that result in no permanent damage to the game nor console, and simply require the player to turn the console's power off to play the game again, though they will result in any data between the crash and the last time the game was saved being lost.
In the Super Smash Bros. series
As with any other game, crashes can occur in the Super Smash Bros. games. It's very rare for crashes to occur from normal ingame play, though glitches and hacks can cause them.
In Super Smash Bros.
Since the Nintendo 64 was a cartridge-based system that could have difficulty securing a connection between it and its game, the connection between it and the game was far easier to disrupt, with a gentle touch of the console being potentially enough to disrupt the connection and crash the game. As such, Smash 64 was far more prone to freezing without the aid of hacks than its successors. Aside from hacks and physical disruption, the game is highly stable, and no surefire ways to crash the game are known.
In Super Smash Bros. Melee
Unlike the Nintendo 64, the Nintendo Gamecube was a disc-based system that was notoriously durable and could effectively keep inserted games in place. As such, freezes in Melee from a connection disruption were rare. When crashes do occur in Melee, the game will completely freeze and cease all response to any input, though any ingame music playing when the crash occurred could keep on playing.
While Melee could occasionally lag the Gamecube in certain circumstances, it was never CPU-intensive enough in normal play to crash the system. However, "black holes" created from the black hole glitch strained the system to an exorbitant amount, heavily lagging the game when they're in play. If players create more than one black hole, or create a more intensive black hole (such as putting more Turnips in it or using multiple PK Fires on it), they heavily risk crashing the game, and will inevitably do so if they keep on making more black holes or keep putting more stuff into one.
A couple of other glitches can also cause Melee to crash. Playing as Master Hand through the Name Entry glitch is notorious for causing crashes through many scenarios, as since he was not supposed to be playable, he lacks many of the assets other playable characters require (such as a victory screen, which results in the game invariably crashing if Master Hand wins a Vs. match). Potentially due to how Zelda technically takes up two character slots (one with her, the other with Sheik ready to be switched to), Master Hand will also crash the game if used in any Vs. match involving her. Another lesser-known glitch capable of crashing the game is the Shadow glitch; the Shadow glitch allowed players to catch the mini-Shadow Balls thrown during Mewtwo's forward throw as if they were an item, and if a player who caught one threw it without it being immediately caught by another player, it would crash the game. However, since the glitch was discovered early on, it only exists in Version 1.0 of Melee, as it was fixed in subsequent versions.
Crashes can also occur from attempting to improperly access incomplete data with an Action Replay. The most well-known example of this is trying to access normally inaccessible uncompleted stages through the Debug menu, particularly AKANEIA. Additionally, if a player uses an Action Replay to play as Sandbag, they will crash the game if they attempt to perform any attack with Sandbag, as it has no attacks programmed in.
In Super Smash Bros. Brawl
Like Melee, console hardware-related crashes are rare in Brawl, as the Nintendo Wii is easily capable of keeping a connection with its inserted game in place, and can handle anything that can occur normally in Brawl. When crashes do occur in Brawl, the game will freeze up and cease all response to any input as usual, but all ingame sound will also be frozen, resulting in a buzzing noise that will play until the game is turned off. Additionally, when crashes occur, the Wii must be hard resetted by holding down the power button until the Wii turns completely off; just pressing the power or reset button will have no effect.
Players typically experience crashes in Brawl from improper use of hacks. One of, if not the most, common means of crashing players experience is when they have the Smash Stack file on their SD card, without running a code that disables custom stages from being loaded, and then going to the stage select screen; the game invariably crashes in this scenario on the stage select screen, as it tries to load the Smash Stack file as if it were a custom stage. Outside that novice mistake, crashes commonly occur from players placing their hacks improperly on their SD card and then trying to access the hack ingame (such as by placing a hacked stage based on Smashville over Lylat Cruise instead of Smashville, and then going to Lylat Cruise ingame trying to play on the stage). Crashes can also commonly occur when a specific hack or code itself is unstable or simply not properly made (hacks of Pokemon Trainer's Pokémon and other transforming characters are especially susceptible to causing crashes, and some texture hacks will crash the game when spontaneously loaded ingame, such as during multi-man matches). Crashes also commonly occur from playing in some single-player modes where the hack/code is unstable or simply unable to be used in such modes (the Subspace Emissary is particularly notorious for how unstable it is with hacks in play, to the point that the Project M team decided to completely disable access to the mode in Project M).
Like in Melee, a few glitches are capable of causing crashes. The most notorious such glitch in Brawl is the grab-break glitch with Yoshi, where if a player grabbed by Yoshi manages to break out of the grab before going into Yoshi's mouth, as soon a the player breaks out of the grab, the game will instantly crash (likely due to Yoshi still trying to access "the grabbed opponent", or not knowing what to do if his grab is broken at that time). The glitch's infamy is from the fact that unlike other game-crashing glitches, it can occur in any match involving Yoshi without any outside elements, and through normal play instead of through a complicated and unnatural procedure that wouldn't be done by a player not trying to intentionally cause the glitch; thus it has the potential to crash the game in the middle of a tournament match without intentional invoking, resulting in either disrupting an ongoing match or forcing one of the players to be disqualified to no fault of their own (and in the potential ban of Yoshi from competitive play). However, since the time between Yoshi's grab connecting and going into Yoshi's mouth is so small, it can only occur at extremely low damages and only with exorbitant mashing skills, thus it doesn't actually occur in normal play and is a virtual nonfactor in tournaments. Another glitch capable of causing a crash is the Chain Jacket glitch; the game will invariably crash if Sheik performs the glitch without having used a prior move. While this can occur in any match involving Sheik, a Sheik player would have to be intentionally invoking it to crash the game through it, thus the only tournament consequence of it would be the forced forfeit of the Sheik player causing it.
Another means of causing crashes in Brawl is the disc itself being damaged. Several players with damaged discs have been permanently unable to access certain characters and stages as the Wii could no longer read them off of the disc; this results in any matches on the disc involving the afflicted characters or stages instantly crashing the game (or even crashing the game if the afflicted characters and stages are even hovered over on the select screens). A damaged disc could only have one specific character unable to be read anymore, or up to a significant portion of Brawl's cast and stages being completely inaccessible. When this occurs, the afflicted player has to get a new Brawl disc, have the disc repaired, or use the file replacement hack to simply load the default files through the SD card instead, though proper handling of the disc will prevent it from happening in the first place.