Halo Night was a recurring event in which Leonard, Sheldon, Raj, and Howard spent an evening played Halo together. It is featured in one episode ("The Dumpling Paradox") and mentioned in another ("The Plimpton Stimulation").
The Halo Night usually starts at 8 pm every Wednesday evening with a pizza break.
In "The Dumpling Paradox", when Howard refused to join, the guys managed to have Penny to take his place. She proved to be very talented at Halo. She "killed" Sheldon at least three times, once with a Covenant Plasma Grenade and another with an Incendiary Grenade. Sheldon was known to be both a sore loser and a cocky winner. The next Halo Night, in which Howard rejoined them, Penny and her friends walked in on the group and said " Hey guys my friends and I got tired of dancing so we came here to have sex with you." The guys continued playing completely oblivious to what Penny had just said.
The depiction of Halo in "The Dumpling Paradox" is inaccurate: Penny asks once, "Hey, whose head did I just blow off," and once again comments, "Look Sheldon. It's raining you!" However, in no Halo game to date can opponents be dismembered in any way. In addition, the sound effects attributed to the plasma grenade explosions are inaccurate.
In "The Plimpton Stimulation", the Halo Night that was supposed to be held in Raj's apartment was interrupted because of the presence of Elizabeth Plimpton.