The user must enter the booth, take the phone off, then say "What if ____?" , then set the phone down. Once this is done, the user will experience whatever they said. However, the scope of the gadget's power appears to be limited to "current world" (including the entire galaxy) and not the past or future.
- The What-If Phone Box
- Nobita's Great Adventure into the Underworld
- Doraemon: Nobita's New Great Adventure into the Underworld – The Seven Magic Users
- I'll Be the King of String Figure World
- World without Sound
- Mirror-Free World
- Farewell Nobita
- I'm Nobiko-chan
- Suneo's Luxuriously Poor Birthday!
- It is a pun on two japanese words "moshimoshi" meaning hello and "moshimo" meaning what if.