R.E.P.O. | Monster guide: Birthday Boy

The Birthday Boy is a Level 1 monster in R.E.P.O. that spends most of its time wandering the map and inflating clusters of balloons as it goes. It looks like a sickly child in a party hat, and as long as nobody touches its balloons, it will completely ignore you.

The catch is that popping even a single balloon flips a switch. The Birthday Boy knows instantly, from anywhere on the map, exactly where the pop happened, and it comes running.

Behavior

The Birthday Boy roams aimlessly and stops periodically to inflate between one and four balloons at a time, building up to around 31 balloons in total per Birthday Boy on the map. In its passive state it ignores players entirely, though it will occasionally stop and stare at them.

The moment any of its balloons are popped by a player or an object, it immediately locks onto the location of the pop, no matter the distance, and runs straight there. If it spots a player near the popped balloon, it enters a rage state, swinging its arms and dealing 10 damage every quarter of a second. While enraged it turns slowly, so it can be outmaneuvered by circling around it quickly. If a targeted player crouches under an object, the Birthday Boy will crawl in after them. It stays enraged until it is stunned, enough time passes, or the player puts enough distance between themselves and it. Afterward it returns to wandering and starts inflating balloons again.

If the Birthday Boy despawns while balloons are still on the map, those balloons remain. Popping one while it is despawned causes it to respawn instantly at that location. When it dies, every one of its balloons pops and vanishes at the same time.

In levels with multiple Birthday Boys, each one only reacts to its own balloons, identified by its hat and balloon color. There are eight possible colors, assigned in order starting from red.

One quirk worth knowing: if the Birthday Boy inflates a balloon in an invalid location, such as against a door, it pops immediately but this does not trigger a rage response even if a player is nearby.

Hidden usefulness

The Birthday Boy's balloons can be used as bait. Popping one will pull the Birthday Boy to a specific location, which lets you lure it into a convenient spot for an easy kill. Dead players can also pop balloons by jumping into them, which still draws the Birthday Boy to investigate but does not trigger its rage, making this a relatively safe way to redirect it.

The Birthday Boy will not rage if one of its balloons is popped by another monster, only by a player or player-caused action. This means you can occasionally use other monsters as passive balloon poppers without inciting its wrath.

Weaknesses

With only 150 HP and a light weight, the Birthday Boy is not hard to bring down physically. Crucially, it will not enrage if it is stunned, damaged, or grabbed, meaning you can attack it freely without triggering its rage as long as you have not already popped a balloon. If it is already enraged and you manage to stun it, it will forget about its target and calm down. Its slow turning speed while enraged is also a consistent exploitable pattern. Repeatedly grabbing and releasing it causes it to become stationary, which is another easy opening.

Strategy

• Treat every balloon as a trap and plan your movement around them, balloons will never block player navigation entirely but carts and items can get snagged.
• Never sprint or make noise near balloons if you can help it, since other monsters will also investigate the sound of a popping balloon, including the Huntsman, who will fire toward the source.
• If you need to pop a balloon deliberately, make sure you are ready to deal with the Birthday Boy arriving quickly.
• If a Birthday Boy is enraged and chasing you, strafe in tight circles around it to exploit its slow turning speed until it gives up or you can stun it.
• If a Birthday Boy is despawned, avoid its remaining balloons entirely since popping one brings it back instantly.

How to kill

The safest way to kill the Birthday Boy is before it ever rages. Because it does not react to being grabbed, damaged, or stunned, you can attack it freely during its passive wandering phase without triggering anything. With 150 HP and a light weight it goes down quickly from any standard weapon or a few solid melee hits. No special approach is needed as long as no balloon has been popped.

If it is already enraged, stun it first. A single stun ends the rage state immediately, and with its Strength Breakpoint of 4 you will need enough strength upgrades to pull this off. Once stunned it stops attacking, and you can finish it off while it is stationary. Its slow turning speed means you can also kite it in circles and attack from behind if a stun is not available, though this is riskier given its 10 damage per quarter second output.

Popping a balloon to lure it to a specific spot and then killing it on arrival is also a viable tactic when you want to control the engagement location.