Here's a family friendly joke.
Sherlock and Watson went camping in the desert. After they built their campsite and set up their tent, night came and the two went to sleep. In the middle of the night, Sherlock shoved and awoke Watson, who was snoring. As the two were laying there, Sherlock said "Watson, look up and tell me what you see." Watson responded "I see a countless number of stars." Sherlock said "And, my dear friend Watson, what do you deduce from this?" Watson thought for a moment before answering "Well, if we can see this multitude of stars from earth, and the universe is far greater than what we even see, then it is likely that some star somewhere contains life. Is that the answer you were looking for, Sherlock?"
Sherlock sat up and looked at Watson and muttered, "No, you idiot. It means someone stole our tent."
