At the end of Operation: E.L.E.C.T.I.O.N.S., Eggbert Eggleston is revealed to have won the election for fourth grade president at Gallagher Elementary, despite the dishonest Wilson Woodrow's earlier claim that Numbuh 1 had won the election, which was a lie simply made to have him help defeat the Delightful Children from Down the Lane. In that episode, they had bribed Wilson to "fudge" the results and elect them as the president, despite the fact that they were not even a candidate at all.
In Operation: M.E.S.S.A.G.E., Numbuh 2 is called in to deliver a note from Eggbert to Muffy Jenkins. The note is revealed at the end of the episode to read "The Splinter Cell is real", indicating that Eggbert may know more about the Kids Next Door than his dim personality might lead one to believe.
Operation: G.R.A.D.U.A.T.E.S after Numbuh T inserted his genetic material into the KND Code Module.This was seen five minutes into the episode. Eggbert also appeared in Operation: S.N.O.W.I.N.G. as one of the kids who were captured by President Jimmy.
He also appeared in Operation: B.R.E.A.K.U.P. standing in line at the stadium.