This was Commodore's first full-scale computer, and the first all-in-one computer to market (1977). Limited graphics and a poor "chicklet" keyboard limited its success although it did fair well in the US, Canadian and UK education market.
The Pet (I can't be sure of the model, but my guess is the original 2001) is part of Kirk's antique collection.
Would it really still be working after 300 years?
It is there, in the background!
The Pet lies unused as set decoration in the lab.
This is 1985, not 1977!
In the "Maths" episode, a Pet (a "computerised toaster") is offered as a prize in a competition.
The PET is shown at the beginning of the episode where Peter Packard programs it to display "Look Around Yog".
The program is written rather too quickly on that chicklet keyboard.
An renegade general has a secret base in the desert and a PET lurks in its control room.
The research facility has a couple of PET computers.
PETs appear on the Delta Defense Grid, and as a "vidi-screen" in the sick bay of the Searcher.
Buck's suspicions are raised when he sees the green aura on the vidi-screen.
A PET in the 25th century, displaying colour video?
The chief of the local television station has a PET, unused in the corner of his office.
The hijacker uses a mobile communications system to talk to his cronies which is controlled by a PET 2001 keyboard.
The robbers build a working model of the bank to plan their raid, controlling it using a PET 2001.
The monitor, normally integrated into the rest of the machine, has been detached.
A Pet appears at U.N.C.L.E.'s new headquarters.
This Pet is a polished silver colour, which is not authentic.
Tom uses a PET at work and later more PETs appear in various places in the prison.
Rudy is told to become editor of a new newspaper for the base and is given a Commodore Pet to write it with.