Ever notice how "Welcome back!" sounds an awful lot like "Well, come back!"?
So when you return from a trip and everybody says "Welcome back", you should say "I already am back! Jeez!" And then everyone will be like "What's up man, I'm just trying to welcome you back," and you can be like "Oh, sorry. I misunderstood," and then they'll be all like, "How could you have misunderstood? It's not very complicated."