1. A person who pops up on IM at the least expected moment; especially if they pop up right after they said "g2g" and logged off. This is similar to how Rafiki suddenly disappears and reappears at random moments in Disney's 'The Lion King'. Particularly in the scene where Simba is chasing Rafiki through the jungle, prior to Mufasa's appearance in the sky.
2. When you email someone a question, and as soon as you hit send, they pop up on IM and answer your question. This is called "a Cyber Rafiki", or "Pulling a Cyber Rafiki on someone". Just like how Rafiki knows the answers to all of Simba's questions about his father Mufasa.
1. "Bob is like a Cyber Rafiki. He always says he's g2g, logs off, and then he's back online two seconds later"
2. Jim: "I just emailed Heather with that question and she pulls a cyber Rafiki on me".
Larry: "What do you mean Jim?"
Jim: "As soon as I hit send, she answers me on IM. I didn't even know she was online. So, random".