The Knights of the Round Towel are the older cousins and servants of King Sandy. They aided him in his attempts to kidnap and marry Numbuh 3 in both Operation: B.E.A.C.H. and Operation: K.A.S.T.L.E.. In Operation: S.P.A.N.K.E.N.S.T.I.N.E., they were seen carrying King Sandy and Mushi's chariot. Their name is a pun on the Knights of the Round Table of Arthurian legend.
Despite being teenagers, Sandy's cousins earnestly enjoy being his knight servents. They are always dejected when Sandy's mom calls them home. They enjoy teasing people as they noted on Numbuh 4's crush on Numbuh 3 and laughed at his poor excuse.
- They are a parody of the Knights of the Round Table