Birthday boy Blam. [my photo]

Birthday Boy Blam is a short male humanoid with a gray rectangular prism for a head and a darker gray cylinder shaped body. On the cameras, he has a rather simple appearance and face. His face is composed of two dots with a simple line for a mouth.

When Birthday Boy Blam is close to entering the office, he holds a smoking pipe and wears a black monocle, a top hat over his party hat, a bow tie, and suspenders. As explained by Jonochrome, this is when he is replaced by "Kevin Jr.", despite a lack of a "Kevin Sr.".

Jumpscare
One Night at Flumpty's
When he is jumpscaring the player, Birthday Boy Blam's face has completely changed. It is covered by black and grey holes and is a bright purple color. He still has long teeth, although much less than when he is at the door.

One Night at Flumpty's 2
When jumpscaring the player, Birthday Boy Blam appears more fish-like and appears to grasp for the player, similar to Flumpty. His eyes are shiny red, with a circular mouth with the teeth from when he's in the hallway, only more tentacle-like. His teeth seem to be curving back into his mouth when he gets closer to the player, but it may be an optical illusion. His arms are also thicker, appearing to be lavender tendrils of sorts.

One Night at Flumpty's 3
In his Jumpscare, he jumps in front of the player and screams, with his mouth wide open showing a sharp tongue and small sharp teeth. He has four black eyes that seemingly melt into each other.

Personality
The exact identity of Blam is unknown. In the game, he almost does not show any character traits, but in the comics he was shown as an ordinary innocent protagonist who became a victim of his alternative evil double Kevin Jr., who tried for some unknown reason to lure him into a trap.

In One Week at Flumpty's series, Blam is shown to be rather emotionless. Most of the time he is quite calm and speaks in the same calm deep voice.