In Emerald, there is a change to how many of the double battles

Sometimes, you'll be walking in front of a trainer and as usual they will challenge you...
but theres another trainer nearby and they get alerted and ask to join in to the battle
So you have to battle 2 totally different trainers at once. A true test of your strategising as they wont both have Volbeat & Illumise or duos like that
There are many battles in this game which are similar, including some by Team Aqua & Team Magma

 
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