The Arrival

 is the twentieth and final episode of the fourth season and the seventy-seventh overall.

Synopsis
The last episode of season 4 begins as Doc tries to convince an incredulous Church of Tucker's pregnancy. When Doc discloses the truth to Tucker, he does not believe him either, thinking he himself has impregnated someone and invents excuses. Caboose enters the base in tears with the skull, asking for help, proclaiming that Andy is dead. After Caboose explains how he found the skull, Church leave the base.

Meanwhile, Andy plays back the message from Command in English for the Reds. After hearing the generic instructions, Sarge becomes depressed, and while Grif tries to cheer him up, Donut spots Church approaching with Sheila. Sheila then fires, frightening the Red Team, which regroups behind a rock formation. Sarge calls for reinforcements, and Simmons attempts to negotiate a surrender from the Blues. Annoyed, Church explains what has just occurred back at his base. To Church's dismay, Andy lets slip that it is possible for Tucker to be pregnant, as the Alien's race propagates by infecting other life-forms with parasitic embryos. Caboose then calls Church to inform him that O'Malley has moved to another host as the Reds had been using their radios, and that Tucker had his baby. Higher-pitched Alien speech can be heard off-screen. Church returns to Blue Base, and Donut follows him, wanting to see the baby. Sarge stops him, and orders him to wait for the ship being sent by Command. Donut argues that it could be weeks, even months before the ship arrives. A ship then promptly lands on top of Donut.

Trivia

 * This episode aired on April 1, the same day Episode 1 aired in 2003.