Bug

Bugs, are a concept in the MegaMan Battle Network series first mentioned in MegaMan Battle Network 2 with the creation of the Gospel Multibug Organism and fully introduced in MegaMan Battle Network 3 with the Navi Customizer, are errors or glitches in a network system or program, especially in NetNavis. These errors/glitches may cause failures or malfunctions in a system, or a variety of side-effects in affected NetNavis during a NetBattle.

Bugs were (probably) replaced by the concept of Noise in the MegaMan Star Force series, along with the EM Wave technology. But, because of the presents of Cyber Cores in electronic devices, besides Wave Roads, it is unknown if bugs still exist in that time period.

Causes
Even though bugs can be present in any network area or NetNavi, only MegaMan.EXE can utilize their power, and many things can cause bugs in MegaMan:
 * Breaking a Navi Customizer rule: If the NaviCust is not customized properly, then MegaMan will receive a bug. The bug depends on which NaviCust program was used to break a rule.


 * Use of Bug Style: The Bug Style, as its name implies, causes many bugs. The bugs caused by this style can either be good or bad depending on just luck.


 * Bug-causing Battle Chips:
 * Getting hit by: There are Battle Chips (some "PvP only") that can bug the other player. Any NetNavis can get bugs if getting hit by these chip, not only MegaMan. Effects depend on the chip used or occur at random, but unlike the Bug Style, it only cause negative effects.
 * Using: Some Battle Chips cause bug on the user, like the Dark Invisible Dark Chip causes random bugs. The Hub.BAT causes an HP bug that halves MegaMan's HP. This side-effect was no longer present in the Hub.BAT during Battle Network 6.

Bug Fragment
A Bug Fragment (バグのかけら), Bug Frag for short, is an accumulation of bugs, a type of junk data found randomly in the games.

In MegaMan Battle Network 2, the leader of Gospel, Sean Obihiro, was trying to clone Bass.EXE though the use of Bug Frags. This however went terribly wrong and the Bass clone mutated into the Gospel Multibug Organism that started overloading the servers with radiation to almost 600%. MegaMan and Lan Hikari end up defeating Gospel. Later, in the Secret Area scenario of MegaMan Battle Network 3, Bass eventually finds Gospel and fuses with him, after which he survives by absorbing Bug Frags that the player has deposited in the Bug Frag Trader. After 300 Bug Frags are deposited, he appears and challenges MegaMan the next time he enters the Secret Area.

Additionally, starting with the second game, and to the end of the series, Bug Frags are also used as an alternate form of currency, as various 'Bug Frag Traders' appear in the game. Chips and programs sold by these traders are usually rarer in value than those sold by standard merchants, though they are often in an out-of-the-way location.

Obtaining

 * In the second game, Bug Frags were only obtainable through Blue Mystery Data, and only a total of 32 (all of which needed to buy everything from the Bug Frag Shop in KotoSquare) are obtainable in the game without the use of glitches.


 * In the third game, finishing off viruses or bosses with a counter hit from any attack would also yield Bug Frags, and this is indicated by a star after the Busting rank is displayed. One star (countering one virus) yields one Bug Frag, two (from two viruses) yields three, three (from three viruses) yields eight. Finishing a boss off with a counter hit will yield ten Bug Frags. While this means of obtaining Bug Frags is highly exploitable with an easily-countered boss, the Bug Frags serve multiple purposes, like boosting the strength of MegaMan's virus-summoning chips, getting past certain barriers or even unlocking another boss through the Bug Frag Trader.


 * In the fourth game onwards, Bug Frags can only be obtained through Green Mystery Data and in-battle Mystery Data. Green Mystery Data collected outside battle always offers one Bug Frag, while in-battle Mystery Data gives a varying amount depending on the area. Also in the fourth game, starting a new playthrough causes all Blue and Purple Mystery Data to regenerate with different content. All Blue and Purple Mystery Data will yield Bug Frags after all of their contents from the first three playthroughs have been collected.