As much as I like rejuvination and reborn, don't rely on randomness and memes to define characters. Having a level of depth and personality can make them likable. Reborn and rejuvination definitely do this too but, there are those types of characters. Have them react to the situations around them, make them feel like they are real people. Show emotion, define them. For example, look at Cain from reborn. He's written as a goofball, but he's more than that. Down to earth tend to be my favorite. Don't rely on swearing, it can be very juvenial. It's unrealistic to have nobody swear in a real world but not everyone needs to. Always seems forced.