When Launchpad is walking through the bakery, when the Fearsome 4 enters and walk past him Launchpad's feet pass through the Fearsome 4 he walks by them.
Darkwing is also colored as Negaduck right after the real Negaduck bowls him right into the Friendly Four.
When Darkwing comes back from the Negaverse (right as he sticks his head out of the cake)he is wearing Negaduck's clothes. The animators accidentally colored him the wrong color for a split second.
Bushroot: We don't have a secret hideout. Why can't we go to your secret hideout?
Negaduck: Bushroot, if I let you go to my secret hideout, it wouldn't be a secret hideout anymore! The whole reason I have a secret hideout is to get away from the geek squad (Fearsome Five members)! See ya next crime.
Friendly Four: We are the terrors that flap in the night. We are the soap that's cleaning up this city. We are Darkwings Ducks!
Nega-Gosalyn: Keen gear!
Negaduck: Friendly Four, Darkwings Ducks. Different names, same old losers!
Darkwing: Quick, LP, create a diversion!
Launchpad: Okay, how about dying from exhaustion?!
Darkwing: Nah, too subtle.
Darkwing: I am the cholesterol that clogs your arteries!
Nega-Bushroot: Negaduck is Gosalyn's guardian.
Darkwing Duck: Gosalyn's sweet, Launchpad's insane, and Tank's polite?!
Negaduck: See you next crime!
Darkwing: (Sarcastically) I fell into a biiiiiig birthday cake, and now I'm in another universe!
Negaduck: So long, I'm off to create more unnecessary pain and suffering.
The Launchpad of the Negaverse has a bag and drops it on the floor, inside the bag is a toy of one of the Gummi bears from Disney's Gummi Bears.
The Muddlefoot's birthday party theme for Honker is the show Pelican's Island which is a direct parody of Gilligan's Island.
Title: Life, the Negaverse, and Everything
A reference to the line "Life, the Universe and Everything" from Douglas Adams' extremely funny book and radio program: The Hitchhiker's Guide to the Galaxy. A third book was created in this series which used this line as it's title.