Or speedhack 0.2 and play for 10 mins... You don't have to mash buttons at all, just sit there calmly and tap them slowly.

Pico gets done in 3 seconds tops.
Darnell takes ages, but you only use ~30 in game seconds.
Nene is the alphabet, a-z, and you can do that in 3 seconds as well.

Voila, done.

Secrets are:
The bone sticking out of Pico's broken arm.
The small circle in Darnell's Eye.
The large eye in the center of Nene's belly, where her belly button should be.

They are only attainable on Hard though.