Gilgamesh appears in Carnival Phantasm as a comedic reinterpretation of his character from the main Fate series. He flaunts his signature arrogance and sense of superiority, consistently disregarding established rules or conventions. This manifests in declarations like "I AM the rules" when accused of violating Holy Grail War game show or Grand Prix regulations. His self-assured nature leads him to violate the "Golden Rule" during the Holy Grail Grand Prix, demonstrating his contempt for constraints.

His interactions feature exaggerated displays of power. He casually eliminates Lancer (Cú Chulainn), triggering a recurring gag where others react with cries of "Lancer died!" and "You bastard!" This pattern of casual violence occurs across multiple episodes. His pursuit of Saber (Artoria Pendragon) becomes parody, particularly when confronted by Saber Alter working as a Gothic Lolita waitress. Saber Alter defeats him using the boast "I am an elegant gothic lolita waitress, sir!", highlighting his vulnerability within this comedic context.

A child version, "Gil-chan," appears in omake segments and promotional materials, participating in lighthearted activities like receiving gifts. Carnival Phantasm exaggerates his traits for humor, removing the gravitas of his original mythological weight. He serves as a source of antagonistic comedy through rule-breaking, overpowered displays, and recurring jokes centered on his interactions with Lancer and Saber Alter.