Okay, I got tired of getting the Smootchum and Tyroge EVERY TIME I hatched the stupid egg, until I did a little experiment. Before I went to get the Odd Egg from the old dude, I took care of getting the bike and battling everybody from the park to the forest so you have a good long stretch to hatch the egg at. Then go to the guy and BEFORE YOU GET THE EGG you save. When the egg hatches, if it's not the baby you want, try again. Sure-fire way to get Pichu. Works every time. You might have to be patient, since the more commonly hatched ones could hatch several times in a row. Personally, I always thought the egg baby you got was set at the begginning of the game, but this is much better.