The Time Machine initially appears to be a room with a grayish-chrome door. When entered, though, the room has blue-striped pinkish wallpaper, a lamp light, green ceiling, and interestingly, a lever with the words "Future" and 'Past" When the lever is pulled in a direction, it sends the user to the future or past, respectively. When the person travels through time, green flashing lights appear the moment they disappear.
Role in the episode
When Squidward asks SpongeTron and his clones for a way to return to his own time period, the robot leads Squidward to the time machine. When he enters, Squidward decides to flick the switch to the past, ending up in the Prehistoric Era.
Once there, Squidward meets the primitive ancestors of SpongeBob and Patrick; Primitive Sponge and Primitive Star. Their meeting is somewhat calm, but when Squidward finally gets his alone time he desired and starts to play his clarinet, Primitive Sponge and Primitive Star become territorial. They chase Squidward down to possibly attack him, so Squidward frantically runs back into the time machine. In a frenzy, Squidward accidentally breaks the lever off the switch on the time machine, and the machine warps from the prehistoric era.
The time machine malfunctions, and weird things start to happen. The time machine ends up in a computer area with random things flying across the screen like "Asparagus" and "Huh." Then the time machine folds itself like paper while flashing in different colors and finally disappears altogether. This is where the climax occurs.
Squidward finds himself in an empty white void called "Nowhere;" nothing appears to exist there but colored squares that can be lifted when touched. At first, Squidward finally feels that no one can bother him as nobody can be found here, but when he says "alone", speech bubbles containing the word randomly appears. Weird voices then start to echo "alone" in rather disturbing ways. After hearing the voices, Squidward becomes hysterical and searches for a way out of Nowhere. First, he sprints across the screen around 4 times, but realizes that by doing that, he just ends up back into the same spot as before. He then jumps around crazily, but luckily he ends up back in the time machine by breaking the floor.
When he enters the time machine, Squidward begins to admit that he misses Bikini Bottom, and even SpongeBob. Upon saying "SpongeBob," the time machine warps him back to the present time period.
Squidward feels happy to meet SpongeBob and Patrick, summarizing his trip to them. SpongeBob and Patrick then ask if Squidward finally wants to go jelly-fishing with the him, but then Squidward yells at them, asking them "What kind of barnacle-head invented that game anyway?" SpongeBob and Patrick tell Squidward that in fact he was the one who did, and begin to laugh and chuckle. Squidward then says he's "going back," ending the episode.
Despite being very technologically advanced, the time machine appears to be a small room with a control switch.
In SuperSponge, when SpongeBob travels back in time to the Primitive Bikini Bottom, it's mentioned that he used Plankton's time machine and shows a background picture of the time machine in "SB-129." This is incorrect because the time machine did not belong to Plankton, but instead to the Krusty Krab in 4017.
When Patron, Patrick's robotic descendant, teleports inside of the futuristic Krusty Krab, the animation has a similar effect like the time machine when it warps through time.
After Squidward warps to the present, the time machine stays partially out of view from the camera. But after the episode ends, the time machine is never seen or even mentioned ever again. It's unknown what become of it after that.
It is never stated who invented the time machine. It may have been SpongeTron, as he is the one who knows where the room is, but it's not confirmed.