The pandimensional spacecraft computer, also known as Z, is a character first appearing in the episode "Bye, Bye, Fly" in the third season of the 1987 television series.
Baxter Stockman finds the computer inside an abandoned pandimensional spacecraft on Earth. Equipped with an artificial intelligence, the computer helps Baxter Stockman fight the Ninja Turtles and Shredder. He claims to have been lonely over the hundreds of years he was trapped underground, and thus is very attached to the first person he encountered. After the spacecraft falls apart, both are defeated and left stranded in the Dimensional limbo.
The spacecraft computer was still with Baxter Stockman in "Son of Return of the Fly II". He helped Baxter Stockman escape the Dimensional limbo and return to Earth where he helped Baxter capture the Turtles so that Baxter can fight Shredder. Upon finding a Solid Energy Generator, the spacecraft computer had Baxter insert this device into their slot, which allowed them to grow an energy-based body and create various devices for Baxter's use.
However, Krang and Shredder had plans to steal the computer for their own ends. The spacecraft computer was destroyed in the resulting battle when Leonardo self-destructed the Generator, leaving only a broken circuit board that still spoke to Baxter. Baxter flies after Shredder with "Z" but does not get through his portal in time and ends up being stranded in Dimensional limbo again.
In "Revenge of the Fly", Baxter and the spacecraft computer are freed from the dimensional limbo by Krang. He plugged the spacecraft computer into the Technodrome allowing Baxter to take control of it. After Baxter created some mutant insects, the spacecraft computer reminded him that he had forgotten about the Turtles causing Baxter to use his insect minions to capture them. The spacecraft computer was left behind by Baxter and found by Donatello. Inside the Technodrome the computer reconnects Baxter, however it's main computer controlling the Techodrome is destroyed by Donatello. Baxter was seen holding the portable computer when he was knocked into the portal so it's unknown if it's programming survived. He was never seen again after this instance.
Z is available as an accessory for the NECA '87 cartoon Splinter vs. Baxter figure produced in 2020.