Very cool.
Harold Goldbrandsen, by chance?
Jack Black?
Mike Hatcher..?
I'd like to hear more about your relative if you fancy a private chat about it.
The era the characters you mention are from the original early Pizza Time Theater era ( 1977-1979 period ).
The 'baseball hat wearing cat' you mention became 'Crusty the Cat', who was Chuck E.s original sidekick who appeared alongside him at the first two PTTs in CA in 1977 and 1978.
Two versions of his portrait frame encased animatronic were made, and one of them still exists in a private collection.
This character was phased out in 1979 with the introduction of Mr. Munch, who replaced Crusty in his absence.
A creative dispute between the two primary folks handling the characters ( Harold G / designer - Mike Hatcher / animation programmer ) led to Crusty getting the boot in favor of Munch.
Mike wanted a 'Cookie Monster' character, but Harold fought to keep Crusty.
The original Munch concept drawings were done by the teenage daughter of one of the designers working for the Company at the time.
The 'girl singers' were The Warblettes, the 'soul singing Magpies' who were the animatronic characters' official backup singers.
They appeared at all PTTs from 1977 until the mid-1980s, swaying side to side and singing offstage above one of the side doors that typically flanked the stage setup used at that time.
Two primarily looks existed, the original black and white version of the Birds and also a 'Rainbow' version which was also produced starting in 1982.
'Madame Oink' is the other character you mentioned, who in the early 70s looked very similar to Miss Piggy of Muppets fame.
She was a 'Guest' character, who was designed to be interchangeable with the exsiting mechanical figures already installed in Stores.
PTTs would switch out the female stage character every year or so to keep the show fresh, and this involved just switching out the cosmetic outer pieces of the figure and sending a new Show reel.
Madame Oink was the 'Romantic piggy from Paree' and had three design variations over the years, the best being her 1982 version which was rolled out nationally to all exsisting PTTs open at the time.
Here is a short video showing a 1982 skit featuring her as the Guest character at a Pizza Time Theater back in the day.
It also features The Warblettes in their original black and white incarnation -