Joel: Because you used to sit on my head and make Lo Mein farts?
*Cue Frank and Mary absolutely losing it*
From The Alien Factor:
Trace: That was a date. I was on an actual date! Whahahaha- *The character looks down* Uh oh...
*Cute Frank again absolutely losing it*
From Danger on Tiki Island there is the continuation of the Running Gag from MST3K wherein a Jump Scare is often met with the riffers shouting "Surprise!" and singing Happy Birthday, and this particular instance is perhaps the Most Triumphant Example across every riffing medium.