On my second playthrough of White, during the battle against Cheren just outside of twist mountain, Cheren manged to get not one...not two...not three...but FOUR critical hits in a row.... FOUR!!!
At first I sent out Ferroseed against his Unfezant (I really wanted to level up my Ferro as quickly as I could, and so I hoped to Curse+Gyro Ball him to death. At the time, he was also at lv37, so I hoped the level difference would help things along). First turn, Unfezant uses air slash, but does little more than 1/3 damage which is comforting, and Gyro managed to do a fair bit. However, on the second turn, 'Fezant gets a critical hit on his air slash and KOs my Ferroseed. I then sent out my Archen. Unfezant then gets another critical hit, and puts my Archen in yellow health (which in turn, lowers it's attack thanks to defeatist)... and my Archen flinched. So, I switched to Galvantula, but on that turn, Unfezant uses air slash again and gets yet ANOTHER critical hit. Thankfully, Galvantula survived and I can outspeed Unfezant now, and used Electroweb to put an end to it. Cheren then sent out Simipour, who I also managed to outspeed. However, Galvantula's electroweb wasn't quite enough to faint Simipour. And then guess what... Simipour uses Scald, which also manages to land a fourth Critical hit from his team in a row, and puts an end to my Galvantula....ARE YOU KIDDING ME?!
Eventually I took it down with Samurott, who (for the record) also nearly ended up getting fainted by Servine, because I got too cocky and tried to use Megahorn on it....and missed. Talk about bad luck.
I know Cheren's Unfezant has the Super Luck ability, and he's holding a Scope Lens (so effectively, there's a 25% chance of a critical hit), but even so, 3 critical hits in a row from him alone works out to a probability of around 1.56% which is still incredibly unlikely. Plus, for his Simipour to land a fourth critical hit in a row afterwards... if I've done the maths correctly, that works out to just under a 0.1% chance which is a bit rediculous. Cheren really got lucky.