Barrel Roll

A Barrel Roll is an aerial maneuver usable throughout the Star Fox series, in which a winged flying machine, such as an Arwing, makes a complete rotation on its longitudinal axis while following a helical path, approximately maintaining its original direction. It is sometimes described as "a combination of a loop and a roll". The G-force is kept positive (but not constant) on the object throughout the maneuver, commonly not more than 2-3 G, and no less than 0.5 G.^[1]

However, the Arwing does not do a Barrel Roll in Star Fox series, except in Star Fox: Assault. Instead, the Arwing performs a maneuver called a rapid Aileron Roll.

The Aileron Roll is an aerial maneuver in which the aircraft does a full, 360 degree, revolution about its longitudinal axis. When executed properly, there is no appreciable change in altitude and the aircraft exits the maneuver on the same heading as it entered. This is commonly one of the first maneuvers taught in basic aerobatics courses.^[2]

In the original Star Fox game), the player must press L or R button twice to do a Barrel Roll.

In Star Fox 64, the player must press either the Z or R button twice to execute a Barrel Roll. 

In Star Fox Adventures, the player must press L or R until it clicks to do a Barrel Roll.

In Star Fox: Assault, the player has to press the L button, and use the Control Stick to adjust the direction of the Barrel Roll. This is the only time the Arwing executes the actual Barrel Roll maneuver. The Arwing can perform quicker, more constant Barrel Rolls, making it more effective, but enemy firepower can still break through as soon as the ship regains straightness.

In Star Fox Command, the player must drag the stylus side-to-side rapidly in opposite directions to initiate the Barrel Roll. The move then continues as long as the player doesn't tap the screen or the Boost Gauge does not run out. All playable ships can perform the Barrel Roll, depending on how well their boost meter works. This time, the Barrel roll creates a magnetic field which can attract collectible items and Anglar hives. When fighting a mothership or chasing a missile, the starfighters can perform a constant Barrel Roll, which the player steers them through red gates to destroy the mothership or missile.

In Star Fox 64 3D the player must press the L or R buttons twice to do a barrel roll.

In Zero, during the Salvadora battle where the player controls Peppy, he will shout out "Barrel roll!" each time the player performs the maneuver.

Lylat Wars Comic

In the Lylat Wars Comic, Slippy performs the Barrel Roll at the advice of Peppy; this makes reference to the source of the techniques popular meme.

Star Fox: Farewell, Beloved Falco

On Titania, Fox and Falco get into a dogfight after a deception from Captain Shears, leading to both Arwings having to use the Barrel Roll technique. Falco points out that the Arwing is at its most vulnerable just after the Barrel Roll move has finished, this is because the disorientation it causes can make a pilot lose his focus and the sight of his enemy and ship needs a few split seconds to make the next one.

The Arwing from the WarioWare: Smooth Moves microgame is unable to perform the Barrel Roll along with most other Arwing trademark techniques, likely in order to make gameplay more difficult and focus on the stage boss.

In Wii Party U when it tells you what to do in the mini game "River Rollin' it says "Race to see who can barrel-roll themselves upsteam fastest."

In one episode of the TV show Donkey Kong Country, the character Funky Kong says "Barrel Roll'n and Roll'n the Barrel" and then says "Peppy".