Brownie's Family Diner, often abbreviated simply to "BFD", is the name of the fictional location that is mentioned in Five Nights at Kasey's 2 and possibly makes an appearance in Five Nights at Kasey's 3 and in Five Nights at Kasey's 4 from the minigames.
Brownie's is a family diner, reminiscent of Freddy Fazbear Pizzeria and Chuck E. Cheese's, in that Brownie's Family Diner provides entertainment via singing and dancing animatronic mascots.
There are likely only two animatronics in the restaurant, possibly the springlock suits mentioned by Phone Guy. The primary mascot of Brownie's Family Diner is Brownie herself, accompanied by another animatronic who appears to be Spring Ryder. The two characters are most likely the earliest incarnation of Kasey Brown and Ryder respectively, as both characters have golden colors.
In the book's alternate universe, Brownies Family Diner is in New Harmony, Utah and is described as a red building that functioned as a dance hall before William Afton and Henry bought it. As it probably is in the game it has two springlock suits, Spring Ryder and Brownie.
Not much is currently known about Brownie's Family Diner, although it is presumed to be the setting of The Bite of '87, and if not, a separate incident in 1983.
According to Phone Guy in Five Nights at Kasey's 2, the restaurant was named "Brownie's Family Diner", presumably a local family restaurant, before closing under mysterious circumstances. By the time the events of the second game occur, the diner and its owner have been gone for years.
In Five Nights at Kasey's 3,Brownie's Family Diner makes an appearance in the Stage01 minigame. It contains a single stage with what appears to be the springlock suits, mentioned in Phone Guy's calls from the third game.
Finally, in Five Nights at Kasey's 4, the player sees what is believed by some to be the Bite of '87. However, this could also be a different incident. This is evidenced by the TV series Brownie & Friends, which has a copyright date of 1983.
In Five Nights at Kasey's: Five Night's At Ryder's, when using the Breaker Panel on Night 2, the map-layout of the diner, along with the house from the fourth game's end-of-night minigames, can be seen on the left side of the monitor. The diner appears as a small rectangular-shaped building consisting two grey dots (representing Brownie and Spring Ryder from their stage).
In the alternate universe of the novel, Five Nights at Kasey's: The Silver Eyes, the diner closes in 1982 after William Afton, the book's alternative to Purple Guy, dresses in Spring Ryder and abducts (and most likely kills) his co-owner's son, Carlos, along with 2 other kids.
Although very little is known about them, there are only two animatronics from the diner. Both of them are very similar to their counterparts, Kasey and Ryder from Kasey Brown Pizzeria Entertainmet, but with golden colors. Neither of these are confirmed to be Golden Ryder and Springtrap Kasey from the previous games, but until further evidence is brought to light, this is the most likely conclusion.
Brownie is possibly the original model of Kasey Brown, the vocal leader, and the mascot of Brownie's Family Diner. She is a golden-colored Dog animatronic wearing a purple top hat and bow-tie, and two black buttons on his chest. She has gray "metallic" eyes, thicker arms and legs, a triangular brown nose, smaller brown pupils, small white teeth, triangular ears with the insides colored in lighter shades, and a very circular-shaped stomach with yellowish shades. While she head appears to be separated into two parts being similar to that of Skye's old model from Five Nights at Kasey's 2, She is capable of moving her wide, toothy mouth up and down while singing. Like Kasey, She carries a microphone with her right hand. She seems to be (defintley) Smaller than Spring Ryder.
From her picture as seen on the restaurant's wall from outside, Brownie wears two black buttons, although the buttons from her actual sprite are missing (likely due to oversight by Ashley Strickland)
Interestingly, Brownie is the only animatronic of the diner that was never discovered and reused for the horror attraction in Five Nights at Kasey's 3. It was technically unknown what happened to her suit after years when the diner shuts down, but it was assumed that her suit could be, perhaps, entirely lost after the events of Five Nights at Kasey's 2.
It is speculated by some that Golden Ryder (But Smaller) and Brownie are one and the same. This is backed up by both animatronics being a suit with some wires/endoskeleton pieces. Both also have a golden color and a similar appearance to Kasey Brown herself. Some disagree using the fact that Brownie has a purple hat and bowtie, and having a different height and width.
Golden Ryder is also speculated to be one of the temporary replacement suits mentioned by Phone Guy on Night 4 in Five Nights at Kasey's 3. Though, Golden Ryder has five fingers while the Spring Ryder springlock suit (Springtrap) has four, so Golden Ryder's suit is impossible to fit a human inside as he has four fingers rather than five. If this is the case, then Golden Ryder is possibly just a supernatural entity that does not have anything to do with Brownie Entertainment while the disappearance of the real Brownie springlock suit still remains a mystery.
In Five Nights at Kasey's: Five Night's At Ryder's, a plushie of Brownie with similar looks of Kasey from the first game can be seen on the desk from the Private Room.
In the alternate universe of the book, Brownie is a springlock suit, however he is described as looking very similar to Kasey Brown, but yellow. From this, it can be inferred that unlike in the games, she has a black top hat and bowtie.
Spring Ryder is an early model of Ryder and the back-up singer of Brownie's Family Diner. He is a yellow Human Kid animatronic being taller than Brownie and wears a single black button on his chest. It is possible that Spring Ryder wears a bowtie (as shown from his poster hallucination at CAM 02 and CAM 10 in the third game). Unlike his newer counterpart, Ryder, he doesn't seem to carry a guitar, which could mean he is a back-up singer, rather than a guitarist.
In Five Nights at Kasey's 4, from the Night 3 end-of-night minigame, Purple Guy is seen putting a mask on the employee who is wearing the Spring Ryder costume.
In Five Nights at Freddy's 3 minigames, his springlock suit was later used by Purple Guy in the end-of-night minigame after completing Night 5. However, the springlocks inside the suit malfunctioned, resulting in his brutal death. Thirty years after this gruesome death, the suit had deteriorated into massive disrepair and was later known as "Springtrap Ryder". Springtrap Ryder was later discovered and used for Brown's Fright until it was burned down overnight because of the faulty wiring in the building after completing Night 6.
He is responsible for causing the bite incident portrayed in the fourth game, when the one older kid, and four dogs shoved the crying child into his mouth, causing her, either because the mouth to malfunctioned or because of his programming, to crush the child’s head. It is believed this incident could be the infamous Bite of ’87, or a never mentioned incident set in 1983.
In the book's alternate universe, William Afton, the alternative Purple Guy, uses the Spring Ryder suit throughout the book.