Yeah, there's the routine engine and equipment check, but sometimes you should also check your aircraft for hidden furry passengers. Two people flying an open-cockpit glider in Kourou, French Guiana realized that mid-flight when they saw a cat inside the glider's wing, desperately clawing to stay aboard the aircraft.
The pilot notices the cat shortly after takeoff; since the video is edited, we can't be sure how much time the little fella spent in the air. Luckily, all the passengers make it safely to the ground in the end.