Jeffy (full name: Jeffy Jeffy) is a fictional puppet character created by Logan Thirtyacre of the SuperMarioLogan (aka SuperLuigiLogan and SuperBowserLogan). He is the main character in the SuperMarioLogan series of videos since 2016. Jeffy has created controversies because of how infamous he is.

Origin
The first appearance of Jeffy Jeffy was on January 24, 2016, in the video titled "SML Movie: Mario the Babysitter!". The video is about Mario having to babysit a random kid (Jeffy) that was dropped by his doorstep. The video has over 25,706,355 views and 182K views. Originally, Jeffy was only supposed to be a one time character but after seeing the amount likes and views the first video got, Logan Thirtyacre continued to make more SuperMarioLogan video based on Jeffy or having Jeffy in the video.
https://www.youtube.com/watch?v=BV5eUTQQiNs

Controversies
Since Jeffy is a big character in SuperMarioLogan videos, many controversies based on the character have sprouted such as:

Jeffy the Rapper
Jeffy the Rapper is one of the most popular videos to feature Jeffy, having 56,322,072 views and 486K likes. This has caused schools to ban Jeffy because kids were singing the song that was the video, which contained lines such as "Hey daddy, I smack these hoes." and "Stick my pee pee in some Cheerios."

Jeffy's Tantrum
Jeffy's Tantrum was a video that was about Jeffy begging Mario to download a SpongeBob SquarePants game on the App Store, but Mario refuses. This causes Jeffy to act rude around Mario. But later, Jeffy is shown being depressed and even suicidal. One scene involved Jeffy almost hanging himself with a noose. Later after the video was uploaded, a 7 year old boy was taught by the video how to make a noose and tried to hang himself. Due to this, the video is now since taken down.

Good Morning America
In 2017, the American talk-show, Good Morning America made an episode based on Youtubers, specifically SuperMarioLogan. The episode criticized Logan for having videos that looked suitable for kids, but weren't. This was mainly because of Jeffy. Fans later criticized Good Morning America for the fact that they never mentioned parents monitoring their children or the fact that it isn't the content creators faut, it's the parents fault.