Pak E. Derms are creatures found in the Nintendo 64 video game Yoshi's Story. They're, as their name implies, elephant inspired creatures who'll walk around with a large sign in their trunks. They won't allow Yoshi, the game's protagonist, to pass by them, though likewise won't attack him either. Yoshi can, however, perform a ground pound next to one and they'll topple over, giving Yoshi access to the next area. However, Yoshi must do this quickly, because Pak E. Derm gets back on his feet shortly after he is knocked over. Because they are the most simple enemy in the game, they appear only on the first level several times, and make no appearance in any other level.
In Super Smash Bros. Melee, they would appear in the background of the Yoshi's Story stage and were also trophies that the player could collect. In Super Smash Bros. Brawl they played a much smaller role as just a sticker.