Crash Landing on Halo
- Main article: Halo (Halo: Combat Evolved Level)
After boarding a lifeboat, he survived the crash landing on Installation 04, becoming the infantryman at the receiving end of most of Sergeant Major Johnson's shouting and yelling. During the events of the crash landing, he fought alongside John-117, until he was evacuated by Echo 419.
Encounter with the Flood
- Main article: 343 Guilty Spark (level)
- “I have a bad feeling about this...”— Private Mendoza, before the Flood outbreak.
Later on, he was part of Fireteam Charlie, which was led by Captain Jacob Keyes and Sergeant Johnson, to find a supposed Covenant weapons cache that a captured Sangheili, 'Qualomee, had uncovered and disclosed to them in passing.
Instead, the so-called "cache" turned out to be a Flood Containment Facility. Fireteam Charlie was immediately ambushed and, save for Sergeant Johnson, was assimilated into the Flood and turned into Combat Forms. Though Mendoza held off the Infection Forms for a while, unlike his comrades, he was also later assimilated into a Combat Form. Shortly before he was infected, he attempted to flee the area, against Keyes' and Johnson's orders.
A few hours after infection, John-117 found Mendoza in the structure and attempted to communicate with the Marine, unknown that his consciousness was already taken over by the Infection Form. Mendoza attacked the SPARTAN and took three entire Soellkraft 8 Gauge Shell from John-117's shotgun, with the results both "spectacular and disgusting." As the corpse-like horror came apart, John saw that one of the small, spherical creatures had taken up residence inside the Marine's chest cavity and seemed to have extended its tentacles into other parts of what used to be Mendoza's body.
- "Why do we always have to listen to this old stuff, Sarge?" - Private Mendoza, upon listening to flip music.
- "Hey, if the Covenant wanna' wipe out this particular part of my history, that's fine by me." - Referring to flip music again.
- "Everywhere... I don't... there! Mira!" - When the Flood Infection Forms started to appear.
- "Wow, this is loco! I'm outta' here!" - While fighting the Flood Infection Forms.
- "And my mama wanted me to be a doctor!" - After killing some Covenant.
- "I have a bad feeling about this..." - Moments before encountering the Flood.
- There is a glitch in Halo: Combat Evolved that allows you to get back on board the Pelican in the level 343 Guilty Spark. Once the Pelican lands, the player may run around the perimeter of the level, where Private Mendoza stands alone. If stuck with a plasma grenade, his body is thrown surprisingly high and far (almost comparable to when the Sputnik Skull is activated in Halo 2).
- Mendoza disliked flip music, a genre of music which Sergeant Johnson greatly enjoyed, much to the chagrin of his squad.
- Mendoza's line "I have a bad feeling about this," may be a reference to Han Solo's iconic line from Star Wars. However, the line is also used in a similar context in the movie Aliens, right before the marines are ambushed by xenomorphs.