The most obvious way that most websites and critics are poking fun at The Emoji Movie is the recently popularized brown spiral with eyes Emoji. It reminds me of the Clinkers, festering brown blobs that created a toxic mess in Clinker's Cavern. It was a very common "That One Objective"* in Banjo-Tooie. The Rotten Tomatoes consensus, unless it changes soon, was simply a red NO symbol (a red circle with a line through it).
*That One Level is a trope described on TV Tropes as a level, not necessarily the final level, that's the hardest by far, or otherwise inordinately hard. That One Boss is the counterpart for battles specifically against a hardest-by-far boss.