When Red Army first acquires their jeep, its radio is blasting loud polka music without any way to shut it off. Throughout the series, polka music gradually rising in volume becomes an indication that Red Army is about to appear.
It's Tejuano music, referencing Lopez being the mechanic.
Also, anytime the tank fires a shot, any character nearby will shout "SON OF A BITCH!"
Sister's odd stories ending with somebody else responding by saying "Yeah! Wait, what?"
Sarge attempting to get Grif killed for the team.
Church's inability to hit anything with a sniper rifle.
He can't even shoot down a guy point blank.
Tucker's inability to actually obtain a sniper rifle.
Every appearance of Adeptus Mechanicus is accompanied by some reference to toasters.
Horus is always referred to as "F*cking Horus".
Karamazov replies to his right hand man's every sentence with "Be quiet, Dominique!"
Dominique really wants to get some sandpaper cigarettes, and no one ever has any or want to fetch them for him.
Every time Fabulous Custodes appear, they want to take over Kitten's position as Emperor's caretaker. Every time, the Emperor is freaked out by the possibility.
In Rick's Minecraft Tales, creepers are ALWAYS drawn flopping back and forth with over-the-top angry faces. Also, the distorted faces people make, the way Nancy goes LO-LA-LA-LA-LA-LA, that thing with the animal floating away aand blowing up, wow, I've lost count!
Hal isn't paid to work for Bowser.
Steve almost always says "HI GUYS!" when he first appears in an episode.
The Inaudible Thwomp's subtitles will usually change into "???"
Paul Hammerbro throws hammers when angered.
Kamek constantly calls Jeff and Hal (mostly Hal) gay.
Ultra Fast Pony uses "14 Hours Later..." for scene transitions, even where it makes no sense. Also, every time Fantastic Racism comes up in the series, the subtitles assure us "I swear I'm not racist." Every time Mayor Mare gives a speech, a mysterious voice calls from the crowd to heckle her.
Characters in Petera Dzive that drink (or sometimes even touch) a bottle of booze will often pass out and wake up naked in inexplicable places. Double Subversion occurs in episode 16, where the main character Peter wakes up naked and grabs a bottle of booze. He suddenly wakes up fully clothed, only to pick up another bottle and wake up naked again.
The Most Popular Girls in School: Whether or not Ashley Kachadorian is supposed to watch the door, as well as Brittnay being told she gives sub-par hand jobs, stuff happening in the 3rd grade, among lots others.
Weiss being bamboozled by someone Flash Stepping in front of her. First with Ruby, and then with Penny. Also with Weiss, everyone except her being greeted normally - most characters call her "Ice Queen", or "Snow Angel" if they're feeling gracious.