The Lemon is a Thing in Paper Mario: Color Splash. It is found near the end of Indigo Underground on a Brick Block. Once Mario breaks the block, it rolls down a ramp near two Slurp Guys. They attempt to slurp it, but stop when Mario approaches. Beating them allows access to the Lemon. Once the Lemon has been picked up, it is wrung out, refills Mario's paint, and becomes a colorless card. Once it has been used as a card, it returns to its position at the bottom of the ramp. It can also be purchased from the Wringer for 150 coins and sold as an unpainted card for 1 coin. The Peddler Toad can also sell the Lemon to Mario if he talks to him after serving the Mamma Mia Pizza and failing to prepare the steak once for 200 coins. A replica version of the Lemon can be collected from the Battle Spin.
When it is used in battle, the scenery changes to a kitchen with Mario and the enemies standing on a cutting board. The Lemon comes down and gets sliced into wedges. The wedges get squeezed and release lemon juice onto the enemies. After they are done, Mario wipes himself. Any enemies still remaining are blinded by the juice. The player can repeatedly press while the Lemon wedges are attacking to increase the damage dealt.
The Lemon is needed to prepare the steak at Tangerino Grill for the VIP. It must be used after the Salt and Pepper and Charcoal Grill or two "Excellent!" Big Fire Flower attacks. However, using a replica at any point will make the VIP reject the steak for its replica taste. The Lemon can also be used during the battle with Petea Piranha, causing him to fall over.
The Lemon can also be placed into the Prisma Museum, where it can be tested.