Yenndo's appearance is identical to Funtime Freddy's endoskeleton, but with few differences - a lack of "face-frames", having both hands (which would include the lack of Bon-Bon), screw without the hat and yellow irises instead of sapphire blue. He can appear in Funtime Auditorium rarely as an Easter egg and in the Custom Night.
Behavior
Yenndo will randomly appear in the Private Room office in Custom Night. He will then rapidly drain your oxygen, until it's low enough so he can jumpscare you. If he appears in the office, the player must put up the monitor as soon as possible. He will attack you by quickly draining your oxygen. When you can barely see anymore he attacks. Yenndo also helps Bonnet because of him draining your oxygen causing you to not see anything like Bonnet's nose.
He can also appear in Funtime Auditorium as an easter egg. He does not attack the player when appearing, he also doesn't twitch or move.
Jumpscare
In his jumpscare, Yenndo pops up in the player's face, chomping his teeth.
Trivia
The name "Yenndo" is actually a combination of yellow and endo.
Yenndo is believed to be the endoskeleton of Funtime Fredbear and the name Yenndo hints to it, with the name being a combination between yellow and Endo and how Fredbear was the only Yellow animatronic in Freddy Fazbear Corporations during the time era.
Yenndo is partially canon with his appearance in Funtime Auditorium being canon, while his appearance in Custom Night not being canon.
Yenndo is one of the Custom Night exclusive animatronics in the game that appear outside of the Custom Night, the other being Funtime Lolbit.
Yenndo's behavior is similar to the behavior of Golden Freddy from FNaF 1 and 2, and Phantom Freddy (most likely Golden Freddy) from FNaF 3.
However, their behaviors don't likely match with Golden Freddy in FNAF 2 because you have to put on a mask for W. Golden Freddy (FNAF 2). Not by putting the monitor on.
Yenndo is one of the only animatronics not to have a voice line. The others being Funtime Foxy, Minireena, and Lolbit.
Despite being an endoskeleton, he has eyebrows, a nose piece, & cheek-spots unlike Endo-01 and Endo-02.
Though in the "Thank You!" image Endo-01 has eyebrows strangely.
Yenndo can be seen rarely in Funtime Auditorium when the player uses the flash beacon. Though, Yenndo will not hurt the player.
This is the only counterpart of Freddy with his endoskeleton fully visible, and also his counterpart to lacks both a hat, microphone and bowtie.
The other being Nightmare Freddy, but without a microphone.
Though Endo-02 may be a Freddy endo also.
Yenndo is one of Freddy's counterparts to have five fingers rather than four. Others being Funtime Freddy, Nightmare Freddy, Nightmare Fredbear and Nightmare.
Yenndo is the second animatronic in Sister Location to have a repeating jumpscare, the first being Ennard.
When Yenndo is in the office his pose is almost exactly the same as his left pose in Funtime Auditorium.
Yenndo stands at about 5.9 feet tall.
Yenndo is one of five animatronics from the Custom Night to only appear in the office and never seen on any cameras. Three others being Bonnet, Bon-Bon, Funtime Lolbit, and Minireena's second counterpart.
Yenndo is probably the endoskeleton of an animatronic that got scrapped.
It is speculated that Bonnet belongs to Yen
Yenndo in the Office
ndo, as he has no rabbit puppet upon his hand like Funtime Freddy.
Audio
Jumpscare in Custom Night.This is shared with animatronics who jumpscares you in Custom Night (except Bidybab).WARNING! EXTREMELY LOUD!
