suppermariobroth:

In this post, you can see two recordings of gameplay of Super Mario World side by side. Both start at a pipe near the middle of the Chocolate Island 1 level, then the footage on the left goes inside the pipe to get launched over the gap, while the footage on the right jumps over the gap instead. This results in an unexpected difference at the next gap with the springboard: if Mario goes into the pipe, there is a level midpoint tape above it. If Mario does not go into the pipe, the midpoint is absent.

The reason for this is that even though it may look like Mario is immediately emitted back into the level when he enters the pipe, he actually enters a parallel version of the level instead, one almost entirely identical but with small differences such as the existence of the midpoint tape.