Cree: You... You did that for me? After all I've done to you and the Kids Next Door?
Numbuh 5: Yeah, you may be my archenemy, but you're still my sister.
Numbuh 1: We've hidden Numbuh 5 somewhere in our treehouse: a place where you'll never find her. (Cree gets mad and tosses Numbuh 1)
Cree: You better hand her over now before I turn this stupid treehouse upside-down!
Numbuh 1: Go ahead and try it.
(cuts to the scene where the treehouse is now upside-down)
Numbuh 1: Wow. I didn't think you could do it.
V.I.R.U.S. stands for Very Icky Research Under Sea.
O.U.T.B.R.E.A.K. stands for Overflowed Undersea Treehouse Bears Really Extra Awful Kontamination.
Operation: V.I.R.U.S. leads up to Operation: O.U.T.B.R.E.A.K., the first time this happens for a pair of shorts airing in the same half-hour. And both begin at the same location: the KND underwater treehouse.
Abby (Numbuh 5) and Cree's mother is shown in the episode "Operation V.I.R.U.S.", and is either French from France, or French Creole from New Orleans or such.
Operation V.I.R.U.S. is a Cree episode.
Operation O.U.T.B.R.E.A.K. is a team episode.
C.L.O.U.D.C.O.V.E.R. Camouflage the Looks Obscure Undercover Detective Craft On Very Essential Reconnaissance seen in "Operation V.I.R.U.S."
B.L.U.B.B.E.R. Big Lumbering Undersea Behemoth Brings Emergency Reinforcements seen in "Operation O.U.T.B.R.E.A.K."
Numbuhs 74.239 and 20,000 appear in both episodes
We learn that Numbuh Four is allergic to coconut with a reaction to swollen lips.
Maurice (first seen in "Operation: M.A.U.R.I.C.E." ) is Cree's date for the prom and has a non-speaking cameo in the last scene of "Operation V.I.R.U.S."
Twenty Thousand Leagues Under the Sea
Numbuh 20,000 is likely named for the above-titled classic 1869 Jules Verne novel.