▁and ▁also ▁a ▁nur ser y ▁rh yme ▁character ▁himself . ▁His ▁name ▁is ▁a ▁reference ▁to ▁the ▁Jack ▁Spr at ▁rh yme ▁but ▁the ▁character ▁also ▁ful fil s ▁the ▁role ▁of ▁Jack ▁in ▁Jack ▁and ▁the ▁Be anst alk ▁and ▁Jack ▁the ▁Gi ant ▁K iller . ▁Serge ant ▁Mary ▁Mary : ▁based ▁upon ▁the ▁rh yme ▁Mary , ▁Mary , ▁Qu ite ▁Con tr ary . ▁Const able ▁Baker : ▁Jack ' s ▁helper ▁and ▁part ▁of ▁the ▁Nur ser y ▁Crime ▁Division . ▁He , ▁Jack ' s ▁former ▁ser ge ant ▁Alan ▁But cher ▁and ▁G ret el ▁were ▁used ▁to ▁make ▁But cher , ▁Baker ▁and ▁K and lst y ck - Ma ek er ▁(" Three ▁Men ▁in ▁a ▁T ub "). ▁Const able ▁Ash ley : ▁An ▁al ien ▁that ▁can ▁stick ▁to ▁walls ▁and ▁speak s ▁binary ▁code . ▁G ret el ▁K and l esty ck - Ma ek er : ▁For ens ic ▁account ant ▁to ▁the ▁Nur ser y ▁crime ▁Division . ▁She ▁is ▁used ▁in ▁the ▁rh yme ▁" Three ▁Men ▁in ▁a ▁T ub " ▁( see ▁above ). ▁Mrs ▁Singh : ▁For ens ic ▁scient ist ▁for ▁the ▁N CD ▁Super int endent ▁Brig gs : ▁Jack ' s ▁b oss , ▁who ▁plays ▁the ▁trom bone ▁and ▁tried ▁to ▁change ▁his ▁name ▁to ▁" be come ▁more ▁interesting ." ▁Fried land ▁Ch ym es : ▁The ▁Div isions ' ▁most ▁intellig ent ▁of ▁detect ives , ▁who