Practically anytime when Tyler or Donna suffer a series of deaths in a hard level.
Tyler has bad luck with Star Bits. First, he needs to collect 100 of them to feed a Hungry Luma, but thinks he only needs 50, leading to a minor freak out. He later has another one when he discovers that the game doesn't save the Star Bits you collected from a level if you leave without completing the level.
The results of the popularity poll in episode 2. Donna's team had less than 50% of the vote, so it was assumed that Tyler won... except Tyler got less than 20% of the vote. The rest of the votes went into Dorkhorse Candidateswho have nothing to do with the race.
Donna's Mind Screw moment / Kaizo Trap in Loopdeloop Galaxy. She touches the goal ring, causing the shine to appear, but as she does, she falls off the track, killing her. This leads to screaming and the following onscreen text:
A fire bar in the first Bowser level knocks Tyler off and into a bottomless pit, sideways.
Tyler and Donna talk about butterflies while fighting Bowser, and then stop and realize that they're talking about butterflies while fighting Bowser.
The opening dialogue to Episode 7.
In episode 7, an Octoguy blasts Tyler and knocks him straight into the path of a descending Thwomp, crushing him and making him lose a life.
In episode 7, Tyler's Angrish when Donna uses Level Leaver as he's fighting Bouldergeist. He also delivers one of the most... colourful insults of all time.
In episode 8, Tyler repeatedly failing to get up a column of blocks as Spring Mario until he eventually Rage Quits.
In episode 9, they discuss going to PAX, and how Pcull44444 is currently sick. Tyler threatens that he'd better get well before the convention or they'll force him to come there inside a giant hamster ball for quarantine.
Tyler goes back to Ghostly Galaxy to try and get the Daredevil Comet star from Bouldergeist...where Donna immediately incites another Wiiverse Humiliation Conga. A few episodes later, Tyler returns the favor, then starts singing Justin Bieber songs to make it even worse.
Tyler randomly reading out "Fast Foes of Toy Time" in a British accent in episode 11.
Also from episode 11, the word association game...
Tyler: I'll start. "Star".
Donna (immediately): "Sex!"
(Both of them break down laughing)
The laugh track in Episode 13.
At the very beginning of Episode 14: "Hey everybody, this is Donnabellez! And guess what, Starbit Blowout!"
Tyler's decision that they should keep versusing after Galaxy finished and go straight into Galaxy 2. At this point, the usual intro pops up on screen... But with Tyler saying a completely monotone "Two" every time the intro says "Galaxy". At one point, a 4 even pops up.
At the end of Episode 20, Tyler is close to getting a rather lengthy star when Donna asks how close to done he is. Afraid that Donna is going to use a lifeline on him, Tyler starts singing at the top of his lungs to keep her from saying anything until he gets the star.
Episode 21 has Tyler and Donna argue about whether you could tell whether elephants never forget or not, before Donna declares the conversation "irrelephant".