 The given name of each kid is a reference to his/her code name.  Numbuh 5 is Abigail Lincoln (the $5 bill shows Abraham Lincoln).  Numbuh 4 is Wallabee Beetles (the Beatles had four members). Numbuh  3 is Kuki Sanban ("sanban" means "third number" in Japanese). Numbuh  2 is Hoagie P. Gilligan, Jr. (he is the second person in his family  to have the name). Numbuh 1 is Nigel Uno ("uno" means "one" in  Spanish).