The episode entitled "Cradle Attraction" (a play on the title of the tragic story, "Fatal Attraction") is clearly a metaphor for a couple and their love life (or, to get even creepier, a SADOMASOCHISTIC couple's love-life). Chuckie and Megan discover that they love being mean to each other, and throughout the episode, that's how they show affection towards one another. Near the end of the episode, Chuckie goes to find Megan and "put a worm in her hair," but can't figure out where she went. He walks up behind her, and sees her poking another boy with a tree branch (which is how she first showed that she likes Chuckie). Chuckie is appalled and runs away, screaming "Megan, how could you?!" while Megan shouts "Wait, it's not what it looks like!"
Phil even comments "You'd think if she was gonna pick on another kid, at least she'd stop picking on you first." So basically, to translate, Chuckie's girlfriend was sleeping around.
In "Barbecue Story," Angelica kicks Tommy's ball over the fence. Tommy delivers a Rousing Speech to the other babies and his diaper straps came undone and his diaper started sliding off. You can see the top half of Tommy's crotch, and he very quickly pulls up his diaper and his cheeks turned red.
In the movie, Dil pulls Tommy's diaper down while he's talking to the other babies. We see their reactions but special mention goes to Lil's expression of wonder and excitement.
In one episode, Stu is showing the family his slideshow from his vacation. In response, Tommy's maternal grandfather/Stu's father-in-law Boris makes a phone call to Dr. Kevorkian. For those of you who don't get this one, see here.
In the episode "Let Them Eat Cake" Tommy and Chuckie accidentally wander into a bar mitzvah/a Jewish ceremony and an obvious bottle of wine is seen on a table.
From "Princess Angelica":
Tommy: Yeah, "Rapoozle" had a prince climb up her hair almost every night.
In "Twins Pique" near the end the babies break into Phil and Lil's dad's office desk to get his "quackulator" (calculator) among the objects they toss out include a magazine with a woman on the cover in a Playboy Bunny outfit.
An episode of Rugrats has Tommy say he needs something hard and thin to put through the Chinese fingertrap in able to take it off his fingers. He then puts his hands into his diaper... to get a screwdriver, but even so...
Also, Didi is trying to tell Betty that the nakedness is a natural stage for babies to go through. Betty is not sold on this, saying, "The sixties are over, Deed, and we lost!"
The creators actually drew Tommy and Chuckie naked but never put it in a serious episode.
An even better (or worse) line occurred in the episode in which Chuckie became obsessed with playing with an inflatable clown doll named Boppo to the point of ignoring the other babies. Says Phil, "A kid his age should be outside playing with his friends, not sitting alone in his room bopping his Boppo." Cue massive Double Take.
Also, in the movie, Charlotte says that she just knew Didi was going to have a boy, with the following line: "You know what they say: born under Venus, look for a—" (At which point her cell phone rings and interrupts her.)
"The Blizzard" had the babies traveling to the North Pole to have Santa fix Chuckie's toy bus. When they reach what they think is the Pole, Angelica starts to complain about how they couldn't find "No toy factory, no funny elves, not even a lame old reindeer turd!"
In the episode The Odd Couple, Stu calls Chaz to ask him to watch Tommy. Chaz tells Stu he has to go, he's paying two dollars a minute on the other line. Stu says something inaudible, to which Chaz, somewhat defensively, remarks "No, Stu, I'm on the Crossword Hotline!" I wonder what Stu thought he was doing...
If you look real closely on the crossword puzzle Chaz is taken he asks for the answer to number one down. The clue is "Stupid" and 1 across is "Door", and reading down the word dum is already written in...with four more letters needed.
In an episode where the gang tries to "potty train" Spike at the end they all pretend to pee on a tree. The boys are standing up but Lil is crouching.
When Dr. Doozer first looks over the X-rays in "Angelica Breaks a Leg," the folder on top is for an Anita Peepers and is marked "DOA" (i.e. dead on arrival) in bold red letters.
There's a blink-and-you'll-miss-it moment in the episode "Turtle Recall" where Chas is looking at an enormous department store directory, and you see half a word cut off by the screen, "vibra-". Go on, just tell me that wasn't supposed to be "vibrators."
What about "vibrating massage chairs"?
In the episode "Kid TV" Angelica has an infomercial for her own cosmetic which she calls her Beauty Juice. The twins mangle this up as her "booty juice".
In the episode "Special Delivery", Tommy ends up in the dead letter office at the post office and nearly falls down a chute that leads to a pile of unreturnable letters and a human skeleton.
Before that moment though, Tommy arrives there via a mailbag the delivery guy was carrying, and he reads a magazine called "American Baby" which has a Playboy-like centerfold. When he opens it up, he says "Baby!" with awe. Remember, this is a magazine about babies.
In "Reptar on Ice" the babies find a lizard, and a running gag is that they put it down their diapers when their parents are coming to them. When the lizard is inside Tommy's diaper, you can tell Tommy is getting a little more "enjoyment" out of it.
The entirety of "Naked Tommy", in which Tommy decides to stop wearing clothes. You can clearly see his butt, too!
In one scene, Tommy describes what being naked is to Phil and Lil. He shows the front part of him where his genitalia can be seen to the twins (but not at the audience).
Tommy: Don't you see, Phil and Lil?
Lil: Yeah, We see alright.
In the same episode, after the twins strip naked, Tommy says, "Uh, Lil, can I ask you a question?"
Also, Didi is trying to tell Betty that the nakedness is a natural stage for babies to go through. Betty is not sold on this, saying, "The sixties are over, and we lost. So get with the program, alright!"
In the Passover special, Grandpa Boris and Grandma Minka argue over their "vine" glasses from the Old Country.
In Mommy's Little Assets Charlotte's assistant Jonathan thinks an "I love you" directed towards Angelica is meant for him. Charlotte quickly corrects him, saying she's very circumspect about affection towards her employees "after the Clarence Thomas hearings."
In the same episode, since a conservative elderly client is visiting, Charlotte instructs Jonathan to take out the hideous Norman Rockwell painting they keep in the closet to replace the Mapplethorpe. For those who don't know who Mapplethorpe is, use caution when Googling him.
In "The Pirate Light," Stu steps into the shower singing "Yankee Doodle went to town, riding on a pony; stuck his finger da da da..." This is a thinly veiled allusion to the parodies of the song "Yankee Doodle" which go "stuck his finger up his butt" instead of "stuck a feather in his cap."
Sound more like "Stuck his finger in an..."
In the Chanukah special there's a building seen in the background in one scene with "מוהל" ("circumciser" in Hebrew) written over the door. There's also a sign next to the door saying they offer them at a cut rate.
In the episode "Cool Hand Angelica," Angelica is reading comic books while hiding out in the outhouse to avoid doing activities she considers "beneath" her. One of the comics is about a kid with a baseball cap, and is entitled Jimmy Hat. Jimmy Hat is a slang term for a condom.
Rugrats in Paris: When Chaz is looking at potential online dates, the picture of the woman not allowed in Kentucky looks like she's on drugs.
"This is the worst thing that's happened since my mom put me on the bottle!"
Similarly, the Mother's Day episode had Phil and Lil reminiscing about their mother breastfeeding them and we even see a flashback. Granted, she is covered with a blanket, but it is rather rare to see breastfeeding even mentioned in children's shows.
The entirety of "The First Cut" which involves Tommy's first cut,COMPLETE WITH BLOOD. Mind its TV-Y/TV-G rating...
Didi liked to take dubious parenting guidance from Doctor Lipschitz. Read: Doctor Lip-shits.
Angelica's lawyer in "Pickles Vs. Pickles" is seen with a cigar. He doesn't smoke it but Nickelodeon has a strict no tobacco policy.
In the episode "The Case of the Missing Rugrat," Grandpa Lou visits the same lawyer from "Pickles vs. Pickles" who is again shown with a cigar. When the lawyer is looking through the drawers of his desk, a cigar lighter is visible inside, and he throws several coupons at Grandpa, one of which, when paused, is revealed to be a coupon for beer.