Smash Bros. has dozens of items, all of which work in different ways. For whatever reason, one person's copy of the game turns to turn every possible item into a tomato, while still retaining the original item's function. It's the most hilarious thing I've seen all day.
The issue, which is being encountered by Leron Tolmachev, is a strange one. As he describes it on YouTube:
This issue is currently occurring on my girlfriend's 3DS XL. I have tried her copy of Smash Bros. in my 2DS, and it works fine, I've tried my copy of Smash Bros. in her 3DS and the issue only occurs on her 3DS XL with the 1.0.4 patch installed. If we uninstall the patch, the issue goes away, but reinstalling the patch causes the issue to return. I've factory reset the 3DS XL and formatted the SD card, but the issue persists.
Hopefully he can figure out how to fix it. As funny as the glitch is, it wouldn't take long for it to get old and in the way of actually playing the game.