At the beginning of the series, Osmosis "Ozzy" Jones (voiced by
Phil LaMarr impersonating
Chris Rock from the
film), a
white blood cell with an impulsive personality and a penchant for challenging authority, and Drix (voiced by
Jeff Bennett impersonating
David Hyde Pierce in the
same film), a straight-laced and by-the-books
cold pill, pursue a
scarlet fever bacterium (voiced by
Tim Curry). During the chase, the three get sucked up by a
mosquito from their host body Frank DeTorre (voiced by Jeff Bennett) and are transported to the body of a 13-years old
Cuban-American boy named Hector Cruz (voiced by Justin Cowden). After defeating the bacterium and settling into their new home, Ozzy and Drix are hired as
private investigators, vowing to protect Hector's health and guide him through the misadventures of adolescence. Supporting characters include Maria Amino (voiced by
Tasia Valenza), a white blood cell cop who is highly skilled at fighting and also becomes a love interest for Drix; Mayor Paul Spryman (voiced by
Alanna Ubach), the immature mayor of the city of Hector; Chief Gluteus (voiced by
Jim Cummings), a stern muscle cell who serves as the city's police chief and Maria's superior; Ellen Patella (voiced by
Vivica A. Fox), an attorney at law who helps cells find homes in Hector, and who becomes Ozzy's new love interest to replace Leah Estrogen after forever leaving her and Frank; and the Brain Cell Advisors (voiced by
Pat Fraley), advisors who help Mayor Spryman run the city due to Spryman being incompetent in his job. Recurring characters include The
Mole (voiced by
Jeffrey Tambor), a former secret agent who holds information on what is happening within Hector; Dander (vocal effects provided by
Frank Welker), Drix's pet dog germ formed from the saliva of Hector's
Saluki Uno; Christine Kolchuck (voiced by
Kimberly Brooks), a friendly student who Hector has a crush on and looks out for Hector; Travis Lum (voiced by
Rob Paulsen), Hector's classmate and best friend who also looks out for him; Ernst
Strepfinger (voiced by
Brad Garrett in season 1,
Jim Cummings in season 2), a villainous germ who uses a gang of germs and
viruses to carry out his dirty work; Uno (vocal effects provided by Frank Welker), Hector's dog whom he adopted in "Oh, My Dog"; and Hector's supportive parents, Mr. and Mrs. Cruz (voiced by Alanna Ubach and
Joe Lala) who look after Hector's well-being. ==Production==