Firefly/Serenity and Blake's 7
Firefly / Serenity borrows most heavily from B7 series 4.
Here are the borrowings I've noticed:
I'll map B7s4 episode onto the Firefly plot/setting strain.
Stardrive / Out of Gas – In Stardrive, the first 10 minutes depicts the aftermath of repairing the Scorpio after collision with an asteroid. Vila tells a poignant story from his past. In Out of Gas, the ship is immobilized and there are poignant reflections on the character's pasts; how they came to be together.
Stardrive / Serenity Film – In Stardrive, the ending climax sees the crew escape from a secured facility, running from a vicious Motocross gang, driving thru desert terrain in a yellow cargo vehicle. In the Serenity Film - opening action scene is "escape from Lilac"... the crew robs a secured facility and escape from the vicious Reavers in a yellow cargo vehicle.
Headhunter / The Message - both have clever dialogue about "I don't like locked boxes", and both had an outsider infiltrate the group who wasn't who he initially appeared to be, and who ultimately brought danger to them.
Headhunter / Objects in Space - our heroes are stalked through the corridors of their own home base and are split into small groups.
Assassin / Jaynestown - the crew infiltrate a filthy outpost town populated by vermin and oppressed slaves.
Assassin / Bushwhacked - the crew investigate a derelict ship drifting in space; there are dark spooky corridors in which they feel threatened by the unknown factor of whoever might be waiting for them.
Assassin / Our Mrs. Reynolds - the pretty, naive, defenseless woman guest star turns out to be the villain.
Gold / Trash - the crew outsmart & dodge security devices to infiltrate a luxury facility for the purposes of robbery. The final exchange d'enouement takes place in an isolated patch of desert wilderness where the clever female character wins the day.
Gold / Trash – botched robbery attempts: In Gold, the B7 crew have to shoot their way out of the Space Princess and escape across the treacherous linking airlock tunnel. In Trash, Jayne has a treacherous experience while dangling on the linking cable harness. Furthermore, Avon & Soolin’s disappearance from the refinery and later reappearance in Keiller’s office is paralleled & modified via Mal and Zoe’s coy portrayal of a married couple in the small Paradiso mining town.
***Now please understand I love Firefly and am not criticizing Mr. Whedon's work done there. Both shows are awesome. I post this an affectionate nod to underappreciated Series 4, look what it gave rise to.