From TF2 Wiki
Birthday mode, also sometimes called party mode, is a server mode that disables the use of blood and gibs, and instead replaces them with streams of confetti and balloons as well as miscellaneous "silly gibs". In addition, all players appear to wear novelty party hats. It is enabled on servers by using the setting
tf_birthday 1 in the server.cfg file. Birthday mode is automatically activated on August 24, the release date of the original Team Fortress in 1996.
Birthday mode features a full set of replacements for most violent graphics and animations, including sound replacements for critical hits. Instead of the standard crit sound, the sounds of party horns, champagne poppers and people cheering and clapping play. Many of the gibs seen in this mode are used in the low-violence version of the game as full-time replacements. A beach ball also appears in BLU's spawn room at the beginning of the round and may be propelled by most attacks and the Pyro's compression blast.
Soldier Party Hat.jpg
A Soldier with a party hat.
BLU Team Party Hats.png
BLU team donning party hats on Dustbowl.
Birthday mode balloon.png
Balloon particle used instead of blood.
Prop Beachball bday.png
"Happy Birthday Team Fortress" beach ball.
- Main article: Silly gibs
- Fixed bug with holiday date computation that turned on Birthday mode a few days too soon.
- [Undocumented] Added a "Happy Birthday Team Fortress" beach ball that will randomly appear in BLU's spawn at the start of a round when Birthday mode is enabled.
- Added TF birthday replacement models for health kits and ammo packs.
- Added TF birthday Party Hat and Noisemaker.
- The party hats were only designed for the classes' default appearance. If players wear different hats, the Party Hat may clip through them or appear to float over top of them.
- The player cannot see their own Party Hat when viewing themselves in third person, such as while taunting.
- Likewise, the hat will always be visible, even in first person, when spectating another player.
- It is possible to kill another player by propelling the beach ball towards someone at a fast enough rate, regardless of whether the player is on your team or not. When a player is killed through this method, it will appear as if that player committed suicide.