Experiment 033 was the 33rd genetic experiment created by Jumba with Hämsterviel's funding. He was designed to drive nails around Jumba's house, but he will sometimes hammer living organisms as well. 033 and the other first 624 experiments were deactivated and smuggled to Earth by Jumba during his mission to capture Experiment 626.
All of the experiment pods were released and scattered across the island of Kauai.
Back at his ship, Gantu trained and conditioned Hammerface, Thresher, Heat, and Plasmoid by using Experiment 625 for target practice, much to his indignity. The four henchmen experiments were then led by Gantu in an attack on the Pelekais' house, where their boss ordered them to defeat and capture Stitch and his replicas after seeing that he had been split into four.
Hammerface engaged one of the clones in a duel. The clone rolled into a ball and slammed into Hammerface, knocking the latter toward the wall, which he clung to. He then jumped onto the floor and ended the fight by slamming his hammer-like head on the opposite end of the floorboard the clone was on, catapulting him into Gantu's awaiting containment orb.
After capturing Stitch and his duplicates, the five returned to Gantu's ship for a victory feast (courtesy of Reuben), but were interrupted by Lilo, Pleakley, and Dupe. After Lilo tricked Gantu into using Dupe's cloning ability, Gantu used Dupe to clone Hammerface into a hundred replicas. However, as Hammerface's power was divided among them, they all became complete weaklings, and thus were easily defeated.
Presumably after this, they were all sent to Hämsterviel who was somehow able to re-merge the weakling Hammerface clones into the original.
In "The Asteroid", Hammerface was one of the six experiments that Stitch convinced to come with him and Lilo to save Earth from an approaching asteroid. Along the journey, Sparky teased Hammerface by shocking him, angering the latter. Later, the hammer-headed experiment started hitting Kixx on the head, only to be ordered otherwise by Pleakley (who referred to him as "Hammerhead" instead of "Hammerface").
In "Remmy", Hammerface was one of the experiments in Lilo's dream.
Hammerface reappeared in "Snafu", and was freed along with Gantu's other captive experiments by Lilo, Stitch, and several other experiments in a rescue mission.
Hammerface was one of the experiments that were gliding on the screen, but he is 525 instead of 033.
The first 624 experiments, including Hammerface, were rounded up by Leroy and taken to a stadium to be destroyed. However, Lilo, Stitch, Jumba, Pleakley, Reuben and Gantu arrived before the experiments could be destroyed.
Hammerface participated in the following battle between the experiments and the Leroy clones.
The Leroys soon gained the upper hand in the battle but were defeated when Lilo, Stitch, Reuben, and several other experiments performed the song "Aloha ʻOe", which caused the Leroy army to shut down due to the original Leroy's fail-safe.
Hammerface made an appearance in Season 2 of the Stitch! anime along with Spike, Woody, Link, and Babyfier. It is revealed that Hämsterviel reverted these experiments to evil using a recording of Angel's song, thus enabling them to wreak havoc on the island.
- Hammerface is one of the ten known experiments named by someone other than Lilo, the other nine being Gigi, Elastico, Yaarp, Heat, Thresher, Plasmoid, Morpholomew, Shrink, and Leroy.
- Hammerface is Experiment 033. However, in Stitch! The Movie, he is erroneously called 124, most likely due to Jumba's untidy database.
- In "The Asteroid", Pleakley referred to Hammerface as "Hammerhead". Presumably because his head is indeed shaped like a hammer.
- Additionally, Hammerface was seen already activated in this episode, but because "The Asteroid" was out of chronological order, he wasn't officially activated until the episode "Dupe" aired.
- Even though we saw Hammerface in pod form, he was technically activated off-screen.
- In the English dub of the Stitch! anime episode "Link-age", Reuben states that Hammerface's favorite type of sandwich is ham on flatbread.
- Additionally, his number is mistaken for 032, which belongs to Fibber.