JoJo the Idiot Circus Boy (sometimes spelled Jo-Jo) is a notable personage within the Blood series and a recurring character of sorts. Though he has not made any official appearances within Blood, Blood II, or their expansions, he is considered a celebrity within the franchise's fiction, and as a result there are allusions to him within many levels. It is not clear what, if anything, JoJo actually does, though his arena within the Dark Carnival level of the original Blood incorporates a pit of snakes and a tightrope, suggesting that he is a bona fide circus performer rather than a simple circus freak. This legitimacy is further reinforced by posters advertising book signings attended by JoJo, and even the heartless Caleb expresses genuine enthusiasm at the prospect of seeing JoJo in the flesh.
At other times, it seems that JoJo is little more than a pariah and a sideshow spectacle. Ishmael, who is revealed in The Nightmare Levels to have assumed the JoJo mantle at one point, tells that he was so mistreated during this time that the constant degradation weighed heavily upon his psyche, making him more receptive when Tchernobog eventually called out to him. While this may seem to contradict JoJo's earlier portrayals, the fact remains that JoJo is not a single person, but rather a persona assumed by multiple people over a long span of time, and thus the skills and status of JoJo may vary greatly from one iteration to the next. In a similar fashion to the real-life figure Fedor Jeftichew (aka Jo-Jo the Dog-Faced Boy), JoJo the Idiot Circus Boy is portrayed oftentimes as something of a savage, hence the tagline "He's uncontrollable!"
In addition to his role in the Blood lore, JoJo is also a cheat code in Blood, Plasma Pak, and Cryptic Passage. Inputting the "JoJo" cheat activates Drunk Mode, which causes the player's vision to distort and sway heavily for a short period of time, which is identical to the effect of a poisonous spider bite.