We don't know anything about the episode, for all we know it could just be another Brock episode where someone's Pokemon/everyone's Pokemon gets sick and Brock has to take care of them.

Now don't get me wrong, I would like to see Brock go as he's pretty much only there to keep Ash & co. from getting completely lost and starving to death and for the flirting running gag got old somewhere between Johto and Hoenn. However being Brock wants to become a Pokemon Breeder, he hasn't really done much of that except for making Ash's & co. Pokemon food. Him becoming a doctor would surely help him in the breeder department, though of course this makes me ask the question if this is the episode where Brock leaves does that mean he'll be going to a medical school or he's just going to be called a Pokemon Doctor despite not having gone through any official training (not that he needs it, though being official would probably help get the word out about him plus he might pick up a thing or two he didn't know since Breeder =/= Doctor if you can see what I'm trying to say).

As for Brock finding a love interest, personally I would rather have it be someone character-of-the-day instead of a Nurse Joy (or Officer Jenny) unless they really make this Nurse Joy really different from the others. Also, if they have a kid, who's genes would be stronger? Brock's who brothers and sisters look like their father Flint with only a few having the coloring of their mother Lola OR Nurse Joy who family line has it that no matter what the children will be girls and look like their mother (and aunts, grandmothers, sisters, nieces, cousins, and other female relatives)?

Pokemon is Japanese

so nothing that the English dub produces count...EVER...

Where was it hinted that Brock would end up with a character-of-the-day in "Two Perfect Girls"? All that song is about is Brock singing about girls he flirts with, with Nurse Joy and Officer Jenny being the two groups he mostly flirts with.

Ash is also using Heracross against Darkrai. My guess is Pikachu will also be in the line-up somewhere.

... WHAT?

Darkrai is a pure Dark-type, which only two weaknesses are Bug- and Fighting-type, plus Fighting-type resist Dark-type attacks, if anything Heracross is the PERFECT choice to go up against Darkrai. The only reason Darkrai is probably going to win is because it's a Legendary Pokemon thus needs to be pounded the heck out of with its weaknesses before it gets to the point it's about the faint (which is why Staraptor and Infernape will be helpful in this match being both know Fighting-type moves).

Hey, I didn't say Heracross was going to defeat Darkrai (infact, I even said Heracross was probably going to lose since of Darkrai's Legendary status). However I still believe that Ash will atleast knock Darkrai out, though will probably only have a few of his Pokemon left (maximum I would say be half of his team left and at minimum only one) to be wiped out from Takuto's other Pokemon.

Personally I hope it's either Infernape or Staraptor that will be the one to knock out Darkrai and will be doing so by just going berserk on it with Close Combat (which hopefully Infernape will learn).