In one scene, the TV, playing up his Insane Proprietor act, pulls some pictures out of a cabinet. They're pictures of a topless woman with star pasties, but they're only visible for a second.
That might have just been a stylized bikini. (They do make them in that shape.) Still probably counts as Parental Bonus though.
Was changed to a full bikini top in later versions.
In the song "Worthless", the beach car originally sings the line "there were bikinis and buns, there were weenies". While it could just be reading too much into it, in the official soundtrack the line is changed to "there were bikinis and hot dogs and weenies", so apparently someone higher up caught on to the Double Entendre.
One of the most subtle, ingenious examples is this exchange:
Blanky:(to Kirby) You can't fool us! We love you! Radio: Like Mrs. Roosevelt loved her husband.
For those unaware of American politics, First Lady Eleanor Roosevelt was a bisexual who had an affair with President Franklin Delano Roosevelt's female secretary. Despite this, Eleanor remained a firm supporter and friend to her husband even while he suffered from polio which left him ill and confined in a wheelchair. To be fair, it should be noted that the Roosevelts had an open marriage, and FDR had many mistresses Eleanor knew about.
At least in an old VHS copy of the film, Lampy very clearly says, "To the showers!" in his flashback when his bulb burned out and he thinks he is a "goner." It is possible this was edited out of other versions, but you can find the quote listed on the film's Amazon.com page, and its Facebook group.
That could have been an intentional Holocaust reference, but most people are going to think it's a sports metaphor, which could have been the idea in the first place too.
Air Conditioner's line. "Hey, I'm real scared, Kirby. Whaddya gonna do, suck me to death?"
During the "City of Light" song, Kirby goes behind a tree to empty his vacuum bag, and Toaster scolds Blanky for watching. Kirby was obviously doing something synonymous to peeing on a tree.