This, well, this is a tough one. It would have to be...
Operation: D.O.G.F.I.G.H.T.

Operation:N.U.G.G.E.T. i LUUUUV it espesially the music number its HILARIOUS!!!!

@amy23000 Oh my gosh, I just watched that episode a couple hours ago! I love when Numbuh 4 looks all love-struck when Numbuh 3 sings. :)

Either
Op. N.A.U.G.H.T.Y.
Op. S.A.F.E.T.Y.
Op. Z.E.R.O.
Probably Z.E.R.O.

Either Operation: C.A.N.N.O.N, Operation: L.O.V.E or Operation: M.A.U.R.I.C.E.

I also have a soft spot for the episodes that focus around Numbuhs 2 and 5, such as R.A.B.B.I.T and C.L.O.W.N.

...Oh, god, that's a tough question...I like 'em all! But if I had to choose, my top 5 are:

1.) Either Op. L.O.C.K.D.O.W.N or Op. E.N.G.L.A.N.D.
2.) Op. H.A.M.S.T.E.R.
3.) Op. L.O.V.E.
4.) Op. S.P.A.N.K.E.N.S.T.I.N.E.
5.) Op. Z.E.R.O.

Operation C.L.O.W.N
Operation C.H.O.C.O.L.A.T.E
Operation V.I.R.U.S
Operation P.I.R.A.T.E
Operation M.A.U.R.I.C.E
Operation S.U.P.P.O.R.T
Operation S.I.T.T.E.R
Operation J.E.W.E.L.S
Operation D.O.G.H.O.U.S.E
Operation H.O.U.N.D
Operation C.A.R.A.M.E.L
Operation F.O.U.N.T.A.I.N
Operation H.O.S.P.I.T.A.L
Operation E.N.G.L.A.N.D
and... *drum roll*
Operation Z.E.R.O
So there u have it and as u can probably tell, my fav episodes are mostly ones where Numbah 5 is the main character :D

Operation P.O.O.L and Operation W.H.I.T.E.H.O.U.S.E are my faves. The storylines are well thougt out and perfect...Also very creative :)

It wold either have to be POOL or WHITEHOUSE because of the storyboards or

Operation BRIEF or Operation GROW-UP

Operation BRIEF is hilarious! Can't stop watching it.

I also like Operation ZERO.

Operation: I.T.
Operation: G.I.R.L.F.R.I.E.N.D.
Operation: Z.E.R.O.
As you can see each episode includes Numbuh 362 in it. XD