Ok Well To See the mad dog you need to start up delta halo on any diffculty. when you get to the part where you kill the sniper on the leadge where the waterfall is kill him and follow these instructions.

continue to go throught the level as normal until you reach the spot where the beam rifles and the needlers are hanging on the wepen rack that the covent dropships drop. kill the elete and go in the cave behind him and go to the very back. there is a dead marien in there goto the back and look on the wall and look for little dots and you will se a wild hog.

It i think resemble the worthog?

Sorry for the spelling.