Anytime you have a pack of Kirbys gank an enemy. Particularly amusing when it's a minor enemy and you have 10 Kirbys.
"It's ridiculously hot in here. Way too hot to be wearing a cloak."
In one of the American commercials, a boy says "You again?" to Whispy Woods, since he's almost always the first boss in every Kirby game.
In the Level Ate castle level of Dedede Resort, there's a purple cloud wearing a party hat who drops cakes on the ground. Go on, touch a Kirby to one of them. Kirby will swell up and hold his stomach with a small moan. Apparently the cakes are too much for him.