Houston became a founding member of the R&B group Immature, known from 1999 as IMx. The group included Jerome "Romeo" Jones and Don "Half Pint" Santos (later replaced by Kelton "LDB" Kessee), with Chris Stokes acting as their manager. At this period Houston went by the nickname "Batman". The group released four albums under the name "Immature".
In 1999 the group underwent a name change but continued on to release two albums under the name IMx: Introducing IMx (1999) and IMx (2001). The group also branched out into film (such as House Party 4: Down to the Last Minute) and television (such as A Different World) before disbanding in 2002.