The best way to get the speed badge is to get all 4 tombtones on top of another and constantly attack them. You will get to the pink castle crasher in about a minute if you can keep the tombstones together and attack the beard at the same time as all the tombstones.
Mission 3 could have its difficulty turned down a bit. Ive done about 200 side missions to build up my army and whatnot, and I still cant beat the boxer. He hits too hard, even my "tank" chars that use the best chars I have get 1 shotted.
I keep experiencing a glitch: sometimes when i click to release the virus, instead of 8 pixels popping out, only between 0-3 pop out in random directions.
I love this game. I am probably alone but I don't have an issue with the achievements because every single game is winnable. You just have to take your take and think about the numbers.
Really good, 6 differences is still my favorite though. I love the music you put in all of your games. Could listen to the tracks for hours. Serene, calming, tranquil, mellow.
 "Castle Crashing \"The Beard\""){kind=icon}
 "My Little Army"){kind=icon}
 "Music Catch"){kind=icon}
 "Infectonator : World Dominator"){kind=icon}
 "Loondon"){kind=icon}
 "ClueSweeper"){kind=icon}
 "4 Differences"){kind=icon}
 "6 Differences"){kind=icon}
 "Mastermind: World Conquerer"){kind=icon}