X-Files: Season 1, Episode 23: "The Erlenmeyer Flask"
Early introduction to hybrid experiments. A scientist (William Secare) is transformed via gene therapy into a hybrid with green blood, super healing, and the ability to breathe underwater. Features a lab creating human-alien hybrids/fetuses. This sets up the entire DNA-mixing conspiracy.

Season 2, Episodes 16–17: "Colony" / "End Game" (two-part story — strongest match for "aliens among us who look like humans")
A series of human-alien hybrid clones (the Gregors and Samantha Mulder clones) live and work as ordinary people (e.g., in abortion clinics harvesting fetal tissue for more experiments). They have alien DNA and bleed green blood when injured. They are hunted by the Alien Bounty Hunter — a powerful shapeshifter who assumes perfect human disguises (including FBI agents) to operate undetected on Earth, kill the clones, and enforce alien rules. The bounty hunter has green toxic blood, god-like strength, and is nearly invincible except for a weak spot at the base of the neck. This directly shows aliens embedded in human society looking identical to us, plus humans carrying alien blood.

Season 3, Episodes 9–10: "Nisei" / "731"
Mulder infiltrates a train carrying a live human-alien hybrid experiment (part human, part alien, with extraordinary healing). Involves Japanese scientists continuing hybrid research from WWII. Explicitly features a hybrid subject with alien physiology.

Season 3, Episodes 15–16: "Piper Maru" / "Apocrypha"
Focuses on the black oil alien virus infecting and possessing humans. Infected people become hosts or vessels for alien gestation. Shows how the alien "essence" (black oil) literally gets inside humans and takes control — a form of humans with alien blood/viral material.

Season 5, Episodes 13–14: "Patient X" / "The Red and the Black"
Cassandra Spender (Cigarette Smoking Man's ex-wife) emerges as a key figure after repeated abductions and experiments. Features the Alien Bounty Hunter again, outbreaks of black oil, faceless alien rebels, and hybrid-related violence. Ties into the ongoing program of creating successful hybrids. Gibson Praise (a boy with natural alien DNA who can read minds) also appears in this arc.

Season 6, Episodes 11–12: "Two Fathers" / "One Son"
The hybrid program's climax. Cassandra Spender is revealed as the first successful human-alien hybrid (her wounds ooze green fluid that heals instantly). The full Syndicate-Colonist deal is exposed: hybrids for survival and slavery. The bounty hunter is involved, and alien rebels attack to destroy the project. This is one of the clearest statements of the "humans with alien blood" endgame.

Additional Related Episodes & Context
Season 4, Episode 1: "Herrenvolk" (follow-up to Season 3's "Talitha Cumi"): Jeremiah Smith, a shape-shifting hybrid/healer from a clone series, is hunted by the bounty hunter. Features child hybrid clones working as ordinary-looking agrarian workers.

Season 5, Episode 7: "Emily": Scully's hybrid daughter (created from her abducted ova) exhibits green blood and hybrid traits.

Seasons 8–9: Supersoldiers (e.g., Billy Miles and others) — humans transformed or replaced with alien DNA/tech. They look completely human but are nearly immortal alien agents.

Q.....confirmation