Does anyone know how to make a character from one video walking into another video?

viviankwarren Posts: 3 Just Starting Out*
Hi, I saw a Disney clip on two different videos put together like split screen and one character from one video walks into the other video then back to their first video. I would like to do that effect but not sure how to. I appreciate any help you can give me. The following is the Youtube address where I saw this effect.