Season 4 Episode
- Season 4 Bionic Rebellion (1)
- Season 4 Bionic Rebellion (2)
- Season 4 Left Behind
- Season 4 Under Siege
- Season 4 Bionic Dog
- Season 4 Mission Mania
- Season 4 Simulation Manipulation
- Season 4 Forbidden Hero
- Season 4 Spider Island
- Season 4 Spike vs. Spikette
- Season 4 Lab Rats vs. Mighty Med
- Season 4 Space Elevator
- Season 4 Bionic Action Hero (1)
- Season 4 Bionic Action Hero (2)
- Season 4 One of Us
- Season 4 Bob Zombie
- Season 4 Human Eddy
- Season 4 The Curse of the Screaming Skull
- Season 4 On the Edge
- Season 4 Ultimate Tailgate Challenge
- Season 4 And Then There Were Four
- Season 4 Space Colony
- Season 4 The Vanishing (1)
- Season 4 The Vanishing (2)
Lab Rats - Season 4 Episode 21 And Then There Were Four
8.08 22 minutes Everyone is shocked when Douglas introduces a fourth bionic sibling named Daniel who’s been living a normal life with an adopted family. Daniel later comes to the academy to meet his father, uncle, and cousins. After Daniel's bionics are accidentally activated by the Lab Rats, Donald and Douglas find out what happened they have to come clean to Daniel about his power-replicating abilities. Daniel also finds out that his cousins are actually his biologic siblings. Filled with anger, Daniel goes out for air on the beach, where Leo and him have a conversation about Douglas. Not too long after, Daniel, using Leo's abilities, accidentally causes a leak in the hydro-loop's fuel tank. After Adam and Daniel combined their powers to stop it, Douglas apologizes to Daniel for lying and Daniel decides to give Douglas a second chance.
