Run into oneself in a dream and you'll definitely wake up.
If one runs into oneself and you don't wake up, just look down at your waist. If you're wearing an obi (お) you know it's a dream and you'll eventually wake up. If you aren't wearing an obi then it isn't a dream and you don't have anything to wake up from.
Currently there are no similar looking kanji which exist in the WaniKani learning system