How To Get An Egg In Platinum From Daycare?

Put in a male and a female of the same type, electric, water, fire, ect...
Or do the dido thing.

First, go to the pokemon mansion and talk to the main guy until he mentions a ditto (soft reset if he doesnt). Second, Put ditto in the daycare with whatever pokemon you want to breed. Third, walk around until the daycare man is facing to his right (or use the day-care checker poke-app).