Crow's script "Earth vs. Soup" has been mentioned before in past episodes and would be mentioned again in later ones (it even gets made (sorta) in a later one). His other script, "Peter Graves Goes to the University of Minnesota" is also brought up.
Mike's sailor suit (which he always wears when performing, whether the role calls for it or not) was last mentioned in Outlaw of Gor.
Corpsing: Trace Beaulieu loses it during the helicopter landing scene.
Hand Wave: When a viewer asks Servo why his head can't be seen through in the theater (note, the puppet used is actually painted black)
Mike chastises Frank for refusing to produce Crow's scripts, saying he wants nothing to do with him, until Frank reveals he's booked him to tour in Cole Porter's Anything Goes for a hefty sum, after which Mike is seen wearing a sailor suit and singing songs from the musical.
When Mike enters the theater still wearing his sailor suit, Servo castigates him, telling him, "Look at you. You look ridiculous." This while Servo is still wearing a Reebok on his head.
Throw It In: invoked Crow's eyes and head weren't supposed to blaze as they did, but Trace Beaulieu's improvised screaming was so funny they kept the take.note The full take can be seen on the "Poopie" collection; the broadcast edit cuts to logo before Jim Mallon pops up on-screen to extinguish him, and fades the audio over crackling sounds before Kevin's laughter trails off.
Tongue Twister: "BartFargoBartFargoBartFargo..." On one of the instances, Crow messed up and laughs.