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On May 9, 2014, Disney XD announced that they renewed Lab Rats for a fourth season . There will be 26 episodes this season . Filming started October 2014. The first episode was released on March 18, 2015.
- Bionic Rebellion (403/404) - March 18, 2015
- Left Behind (401) - March 25, 2015
- Under Siege - (402) April 1, 2015
- Bionic Dog (412) - April 8, 2015
- Mission Mania (405) - April 15, 2015
- Simulation Manipulation (406) - April 22, 2015
- Forbidden Hero (408) - July 1, 2015
- Spider Island (409) - July 8, 2015
- Spike vs. Spikette (407) - July 15, 2015
- Lab Rats vs. Mighty Med (415) - July 22, 2015
- Space Elevator (414) - July 29, 2015
- Bionic Action Hero (410/411) - August 5, 2015
- One of Us (416) - August 12, 2015
- Bob Zombie (417) - September 30, 2015
- Human Eddy (419) - October 14, 2015
- The Curse of the Screaming Skull (420) - October 21, 2015
- Lab Rats: On The Edge (421-422) - November 11, 2015
- Ultimate Tailgate Challenge (413) - December 2, 2015
- And Then There Were Four - (418) - January 13, 2016
- Space Colony - (424-425) - January 20, 2016
- The Vanishing - (423 & 426) - February 3, 2016
- Billy Unger as Chase Davenport/Spike
- Spencer Boldman as Adam Davenport
- Kelli Berglund as Bree Davenport/Spikerella
- Tyrel Jackson Williams as Leo Dooley
- Hal Sparks as Donald Davenport
- Cole Ewing as Sebastian
- Max Charles as Spin
- Brandon Salgado-Telis as Bob
- Jeremy Kent Jackson as Douglas Davenport
- Maile Flanagan as Terry Perry
- Grace Kaufman as Kerry Perry
- Angel Parker as Tasha Davenport
- Michaela Carrozzo as Caitlin
- Jessalyn Wanlim as Giselle Vickers
- Ashley Argota as S-1/Taylor
- Mateus Ward as Marcus Davenport
- Will Forte as Eddy/Human Eddy
- John Eric Bentley as Mr. President
- Pearce Joza as Daniel Davenport
- Graham Shiels as Victor Krane
- Marissa Cuevas as Lexi
- Joel Michael Kramer as Tank
- Jumpy the Dog as Otis
- Judith Drake as Mrs. Stern
- Liana Ramirez as Kate/Spikette
- Mar Mar as Reggie
- Ryan J. Kelly as Thermo Hands
- Damion Poitier as The Incapacitator
- Mark Saul as Dr. Ryan
- Leo Howard as Troy West
- Emery Kelly as Logan
- Ping Wu as Dr. Gao
Special Guest Cast
- Bradley Steven Perry as Kaz
- Jake Short as Oliver
- Paris Berelc as Skylar Storm
- Carlos Lacámara as Horace Diaz
- Jilon VanOver as Tecton
- Jenelle McKee as Gamma Girl
- Esteban Cueto as Gray Granite
- Willie McGinest as Himself
- This season is renamed to Lab Rats: Bionic Island. It also features an updated beginning to the intro.
- This season makes Lab Rats the 2nd Disney XD series to make it to Season 4.
- There were five one-hour episodes (not including the crossover): Bionic Rebellion, Bionic Action Hero, Lab Rats: On The Edge, Space Colony, and The Vanishing. This is the most one hour episodes in a season.
- Spike returned in Spike vs. Spikette, along with another student with the Commando App (Spikette) and Bree's Commando App, (Spikerella).
- Leo was given a bionic leg to replace his injured one in Space Elevator.
- There was a crossover this season with Mighty Med in Lab Rats vs. Mighty Med.
- This season features two new sets, the Mentor Quarters and the Davenport Bionic Academy.
- Hal Sparks directed the episodes Left Behind, Spider Island, and Space Elevator.
- Marcus Davenport, Taylor and Victor Krane all return this season after the latter two were presumed deceased, while the former was brought back to life after being destroyed.
- Of the three, Taylor is the only one still alive.
- A new bionic sibling is introduced this season, Daniel Davenport.
- The season and series finale, The Vanishing, aired February 3rd, 2016.
- This is the only season that doesn't end in a cliffhanger.
- This is the only season that Rose, Janelle and Trent don't appear.
- Janelle was however mentioned in One of Us.