Your Pokemon's happiness can increase by doing the following:
Pearl and Platinum
you must have a bunnery and it evolves to lopunny by happiness. giving it massages from the lady from veilstone, leveling it up in battles, poffins, and holding the soothe bell will improve so.
happiness+nightime
evolve togepi with happiness
Level up with max happiness
You have to evolve BUNEARY with full happiness.
It evolves via happiness
It means thAt. That Pokemon is at maximum happiness and if youcan answer this , where can you find a happiny in any of the three Pokemon games ( platinum pearl or diamond )
it evolves by happiness in every game its in.
You evolve it by raising it to maximum happiness.
You have to train an Eevee by happiness at night
EVolve an Evee from happiness at night time.