Bugs:Pokémon Ruby and Sapphire

This page details bugs of Pokémon Ruby and Sapphire.

Protect Bug

Protect, Detect, and Endure are moves that will always succeed on the first use, but have a halved success rate with each consecutive use. Rather than calculating the probability on the fly as earlier generations did, Generation III uses a fixed table that contains probabilities for the first four consecutive uses (100%, 50%, 25%, and 12.5%, respectively). Apparently, Game Freak did not anticipate that someone might be lucky enough to successfully use Protect four times in a row, as the fifth and any consecutive uses will read the data that comes after the probability table, leading to very erratic and seemingly random success rates.

A complete table can be found here. Note that starting from turn 53 the values differ between Ruby & Sapphire, FireRed & LeafGreen, and Emerald.

Ruby & Sapphire have an additional bug: Protect, Detect, and Endure have a 1 in 65,536 chance of failing even when the move should succeed (including on the first use) due to the wrong operator being used. This was fixed in FireRed, LeafGreen, and Emerald.

National Pokédex bug

While obtaining the National Pokédex in any of the mainline Pokémon games usually does not require event-exclusive Pokémon, Ruby & Sapphire have a bug and exclude Chikorita from the National Pokédex requirement instead of Ho-Oh and Lugia. Both Pokémon can only be obtained as trades from Pokémon XD: Gale of Darkness. This was fixed in FireRed & LeafGreen and Emerald.