The Shrinking Machine is an invention of Phineas and Ferb.
When Phineas & Ferb and the gang were bored on a rainy day, a boy named Irving, who claimed to be their biggest fan, suggested Hide and Seek. When Buford asked how one would play Hide and Seek in a house so small, Phineas suggested that they used the shrink ray to shrink themselves down.
After shrinking down
Phineas & Ferb and the gang tested out being small while a song played in the background. Afterwards, Phineas told everyone they can play Hide and Seek now, then Candace came in while talking to Stacy on the phone. She noticed the shrinker and told Stacy she'll call her back, this thing was obviously made by Phineas and Ferb so it must do something. She left the house with the shrinker so she could show it to Mom. Isabella showed Phineas that Baljeet was up on the umbrella stand. Candace opened the umbrella and Baljeet got catapulted up. Phineas told Baljeet they would get him out as soon as they got the shrinker back. Baljeet told him he was freezing from the air conditioner.
- Ferb came up with the idea when Buford asks if the house is too small to play Hide and Seek in.