I chose Chimchar, because it's attacks are strong, and I wanted to have a partner from 4th generation, because it's not possible to have one in PMD 1. Also, Chimchar is good against Grass types that are Mudkip's biggest "problems", and I just haven't ever used Chimchar before in any game.
I chose Pikachu because it worked best with my pokemon. I got a Charmander so naturally, the main type I would have to worry about it water, in which Pikachu's electric attacks come in mighty handy. I would have chosen a grass type so it could work on ground types as well, but I just love Pikachu too much. It's so cute.
I picked Turtwig to back up my Chimchar b/e I like the mix of fire and grass. Had that combo in PMD1. Plus I usually only pick pokemon from the same generation. Only acception being Pikachu to back up whatever pokemon is main. Still: fire & water = can't go wrong
I picked Pikachu. I picked it because I was a Mudkip and well, I kinda wanted a Pikachu anyway... Heh.
I wanted to be a Mudkip as a main character and I luckily got it.((Not going on to any websites to get some guide to answer the questions to get whichever pokemon I wanted, I just answered truthfully! Yay irony!))