Blarggity Blarg-Tucker

Season Four
Junior made no physical appearances in season four, but played an important role nonetheless. During Tucker, Caboose, Andy, "Fluffy", and Tex's trip on "The Great Journey", Tucker complains that the Alien is constantly standing over him while he sleeps. Tex writes it off as safeguarding of the sword, while Caboose concludes that the alien is either stealing the humans' sleeping technology to use against them or just stealing Tucker's breath.

Upon returning to Blood Gulch Tucker begins throwing up and becoming moody, much to Blue Team and Andy's irritation. After a while, Church decides to call Doc/O'Malley to find out what's wrong. Upon investigating, Doc claims Tucker to be pregnant. This causes a lot of hysteria among Blue Team as Tucker claims it isn't his, Church claims it to be impossible, and Caboose is worried about it being contagious.

Tucker finally begins to give birth, and while dealing with Red Team, Church finds out from Andy that aliens can impregnate humans with a parasitic embryo, though Church still believes the pregnancy to be impossible. Junior finally appears at the end of season four (though only in voice) saying "Blarg blarg! Honk!" in a high pitch voice similar to Tucker's.

Season Five
In Episode 78 it again appeared in voice only while it was wrecking the base after Doc fed it half a gallon of Caboose's own blood, saying high pitched Honks and Blarghs, Its first visual appearance was in Episode 80 as a mini version of an Elite with teal and blue armor. Church frequently tells himself that he will kill Junior, but never does anything aggressive to it. He also frequently talks about it being gross, despite it never having done anything remotely disgusting. Tucker only reacts to either of these tendencies once, and quickly blames it on hormones when he does.

It appeared in Episode 91, in which Doc was "examining" Sister, but when Tucker found it in the base, it was a lot bigger than the last time we saw it. As Tucker tries to sneak a view of Sister without her armor on, Junior continues to blarg and honk, slightly irritating Tucker.

In Episode 94,Church decides to launch an attack on Red Base based on a suggestion from Vic Jr. Church decides to send Junior, Doc, and Sister through the caves (again, per Vic's suggestion), when Tucker decides to prepare Junior for the rest of his life. After giving Junior some "advice", Tucker finishes by telling Junior to "mix it up a little" with girls, following which Junior says "Bow-chicka-honk-honk," a twist on Tucker's infamous catch phrase, which Tucker attributed to "genetics".

In Episode 99, it was revealed to be the "Alien race savior", who the alien planned to have controlled by O'Malley to control the Aliens and win the war. After Tex beats up Tucker and takes his sword, she ushers the two aliens into the crashed pelican. After infecting herself with Omega, Tex takes the ship to complete Omega's plan, but Andy detonates and blows up the ship, "[scoring] two for red team."

Reconstruction
During Shiela's playback of her crash during Chapter V of Reconstruction, Shiela notes that a hatch is opening, and Tex screams "Where are they going!?!" likely referring to Junior and the other alien, as no alien bodies were found near the crashed ship.

Simmons
Junior interaction with Simmons is next to none, but he does rip his spine out in the PSA "Let's All Go to the Movies" on Tucker's command.

Church
Despite Church's constant insulting of and threats to kill Junior, Junior remains mostly passive towards Church, doing nothing but blarging and honking in his pretense.

Tucker
As father and son, Junior and Tucker share a bond. Despite not knowing how to raise a kid at first, Tucker later found himself looking at minivans and generally "getting into the whole parenting thing." Junior seems to show happiness in being around and talking to Tucker, but was generally too young to show any real signs of family love. It should also be noted that after Junior's apparent death, Tucker simply walked away, saying "Yeah, fuck this!"

Caboose
In return for a cookie and a glass of orange juice, Caboose willingly let Junior drink half a gallon of his blood. After being told to feed Junior again, Caboose timidly said "please no." In general despite Caboose's hate for babies, his relationship with Junior is mostly positive. He even expressed desire to scrapbook after Junior began growing up so fast.

Doc
Junior's first feeding, first words ("honk-honk", or purple), and first walk were all a direct result of Doc. Doc clearly was very fond of Junior, spending time with him a praising him happily. He even decided to send back Church's shower gift as punishment during Church's first attempt to kill Junior. Tucker even considered Doc his first choice as a babysitter.

Sister
Sister's first meeting of Junior was less than flattering for the little alien, she mistook him for a dog but quickly corrected herself by describing him as a "kid that looks like a dog". During her trip through the caves, she was slightly supportive of Junior, calling him cheerily calling attention to him as he fell behind. A deleted scene shows Sister babysitting Junior, where the relationship was shown to be much less positive, as she constantly screamed at him and locked him in the closet and complained about having to feed him.

Production
The Alien baby was created using an unusual technique called forced perspective. According to series creators in the extras of the season 5 DVD set, the Alien baby was filmed by having the Covenant player stand further away, while aiming the camera in such a way as to obscure to feet or pull focus away from ground. This causes the illusion that the alien and other characters (typically Tucker) were standing closer than they were, eliminating depth perception. While this technique worked most of the time, some shots were impossible without some digital editing.

trivia
A similar alien appears at Sandtrap in Recreation. This may or may not be Junior.

A blue elite is among the bodies seen at the end of Lay of the Land after the Elephant Driver