Numbuh 4 (a.k.a. Wallabee Beetles) is a character from Codename: Kids Next Door.
The Grim Adventures of the Kids Next Door
Numbuh 4 appears in Billy's house along with the rest of his team, the Sector V, to try to take Billy's pants from his father, Harold, with the scythe embedded in them. Seeing that did not work, decide with his friends bring Billy to KND Deep Sea Lab to try again.
During the trip, Numbuh 4 was impatient with the antics of Billy until they receive a call from Numbuh 362, who informs them of a strange activity being conducted by The Delightful Children From Down the Lane, forcing the Sector V to deviate from the path. Arriving at the destination, and after the Delightful Reaper is created, and has his evil plan to assimilate everyone. Except for Numbuh 2, the rest of Sector V flees to the KND Moon Base, which inform Numbuh 362 about the Delightful Reaper while see Mandy posing as Numbuh 1, luring nearly everyone.
Once Mandy takes full control of the KND Commando, take Numbuh 3 and Numbuh 4 as her right hands, with whom part in the M.A.N.D.R.O.B.O.T. to face the Delightful Reaper. When Mandy left assimilated by the colossal creature, Numbuh 4 is assimilated at a time, is assimilated at a time, although it is released along with the rest of assimilates as Numbuh 1 and Grim destroy the Delightful Reaper. After that, Numbuh 4 assists stopping Mandy in KND Moon Base along with the rest of Sector V. After Mandy escape, Billy poses as Numbuh 1, so that everyone starts throwing things be responsible for everything that happened.