Specifically, they're the dummy plugs.
Not only do you have to have seen the show, you have to have made it more than half way through the series. My hope is that someone will read this comic, then see the show years later and have a muted chuckle.
These May Exist
Ms.Curious: What's this? Some new anime figure?
Ms.Collector: Huh? Oh, sort of...
Ms.Collector: They're collectable Eva themed butt plugs. Each one contains an accurate scale model of Rei.
Ms.Collector: I guess that's a spoiler