Baby Face (赤ちゃんの顔 Mitsuruo), is the last Keymaster Headdy fights in Dynamite Headdy, and is fought in stage 6.4, which shares his name. Since said stage is the last of the aerial ones, Baby Face can only be fought using one of the three flying heads (all of which are helpfully provided near the start for the player to choose from).
Baby Face takes the appearance of a large head on a metallic stand and has four separate forms that each depict a male advancing through different stages of life; baby, boy, adult, and elderly man. Each form appears only after the previous version has been defeated, with the head moving into the center of the screen before splitting into two to reveal the next form hidden underneath (the discarded halves cause damage to Headdy if he is hit by them).
This boss doesn't have a weak spot; anywhere on his face will do.
- Baby Face - The head lazily moves backwards and forwards across the screen while spitting multiple bubble-like energy balls that very slowly drift in the general direction of Headdy. All bubbles are immediately destroyed upon defeating this first form.
- Boy Face - A hand pointing upwards bursts from the clouds below where Headdy is at that moment, in an attempt to hit him. The finger on the hand then shoots eight bolts of electricity in a spray around itself, then drops down a bit (the hand blocks all of Headdy's attacks except for those of the Rocket Head). This happens three times in total, until the hand is once again under the clouds, so that it can repeat the process. The head itself moves much more quickly across the screen than its infant self, but will stop briefly just before the hand attempts its surprise attack, before moving once again after the first volley of bolts. Both the hand and any bolts on screen are destroyed after this form is vanquished.
- Man Face - This head begins by moving to the far right of the screen, whereupon it starts firing lasers from its eyes. The laser are initially a spread of eight in a semi-circle pattern that covers the screen, but Baby Face will also shoot four additional blasts along the path of one of the nine aforementioned shots; namely whichever one is closest to Headdy. To exacerbate matters, a hand holding a hook will emerge from the clouds to snag a banner from above the stage, then move said banner around the screen to obscure the player's view; the banner doesn't cause any damage, but the hand will. The hand once again blocks all attacks except those from the Rocket Head. Both hand and lasers are destroyed once this form is defeated.
- Grandpa Face - The head stays in the center of the screen while he tries to grab Headdy with an old, gnarled hand that quickly darts in and out of the bottom of the screen. If the Headdy manages to avoid the hand and destroy this final form, the head splits open to reveal Bino tied to the metallic stand that was supporting Baby Face, who can then be shot for a Secret Bonus Point. However, if the hand catches Headdy, then the boss chuckles and suddenly seemingly dies of old age (together with a "wah- wah- wah- wah- wahhhhhh" sound being played in the background), with his spirit flying off before the hand explodes, soon followed by the head.