Rainbow in the Dark is the title of the pilot episode of Rainbow the Mummy Hunter and is
also the title of the theme song, which is a reworking of Ronnie James Dio's song of the same
name.
The fact that this pilot ever got made is astounding. The writer/director (Oliver Kelly) was a
3rd year film student at the University of British Columbia when the pilot was made. He had
began to formulate an idea in his head during his sophomore year about making a show similar to
Buffy or The X Files, but he had no budget and didn't really have a firm direction for the
show. What changed that was a modest lottery win of $10,000.
The director contacted booking agents, attempting to see if he could hire anyone recognizable
for his pilot for the amount of money he had, but he had no luck. A few weeks later he had begun
informally auditioning students for roles when he got a phone call, Jennifer Love Hewitt was
in town and had a personal appearance cancellation and thus was available for one day on his
budget.
The director, still unsure of what he even wanted to do with his show came up with the idea
of her playing the researcher, he wrote generic lines about various monsters and issues and
situations and filmed Jennifer for 16 hours doing them, mostly in the same room at the same
computer desk, with only a few costume changes. They actually ran out of material after a few
hours and the rest of the day they just made things up on the fly. He also spent a few hours
getting some walking and running shots around campus as filler, and figured he had enough
material to write around from that point on.
That one day of filming (for a rumored $6000) was actually almost the entirety of Jennifer Love Hewitt's involvement with Rainbow the Mummy Hunter. They stretched that footage out for three full seasons. The director would use a stand in and film from behind whenever Jennifer's character ("Abby") needed to be onscreen with the other actors at the same time or simply had to do anything they hadn't already filmed. The usual stand in for Hewitt was Donna Copperfield (older sister and personal assistant to the shows leading lady Theresa Copperfield). Jennifer never even met any of her co-stars until the 2000 Gemini Awards where she sat with her co-stars because she had been nominated for "Best Performance by an Actress in a Leading Role in a Dramatic Program or Mini-Series" for the first season of RtMH. After the 3rd season Hewitt expressed interest in joining the show on a more regular basis, however the fourth season ultimately never happened.
From the Hewitt material Oliver was able to put together a pilot script. He had cast his roommate's girlfriend Darlene Wood as the leading lady "Kitty" but he still needed a leading man, enter David Tennant. Tennant was in town doing theater work, but had a free weekend. Oliver encountered him in a bar and the two hit it off. Tennant ultimately agreed to a weekend of filming Oliver's project after losing a drinking contest to him the very night they met. Tennant was actually under the impression that the project was a student film and not a television pilot and didn't find out otherwise for quite a long time.
A lot of people remark on the similarities between the Rainbow character and Doctor Who. Oliver and Tennant both addressed this issue on DVD extras to the 3rd season of RtMH. Oliver said that he had based the Rainbow character rather loosely on Tom Baker's rendition of the 4th Doctor (and refused to comment on the almost identical scarf when Tennant mentioned it in reply). While Tennant commented that it was quite likely that Rainbow the Mummy Hunter both inspired the Doctor Who revival and was directly responsible for his being cast in it. In fact the BBC actually purchased the rights to the show after the 3rd season, but never produced another season. Although many fans have pointed out that "Love and Monsters" from the second season of Doctor Who is only a slightly rewritten version of the unaired RtMH script "Freaky Fan Club" as included in the unused scripts book that came with the RtMH Ultimate Anthology Boxed Set.
The plot of the episode is actually a genius bit of low budget film work. Vancouver keeps getting overcome with a mystical darkness that sometimes lasts minutes and sometimes hours. No lights can pierce this darkness and when it lifts people are always missing. Fully one third of the screen time of the episode shows nothing but a black screen. Rainbow and friends ultimately overcome the problem and are able to restore most of the missing, but some are lost forever.
The fandom is divided over the continuity of this episode with the rest of the series. Darlene Wood's "Kitty" in this episode seems to already be Rainbow's sidekick, while Theresa Copperfield's "Kitty" only meets Rainbow for the first time in the first regular series episode. Additionally the supernatural element of this episode is more overt than even the season 3 episodes and really doesn't fit in line with the first season at all (in which the supernatural elements are often either exposed as false or left relatively unsure). Others in the fandom argue that this episode is simply out of order with the rest of them and fits nicely inbetween the 2nd and 3rd seasons (based off a few lines of dialogue in the season 3 premiere). In either case this episode is never directly referenced anywhere else in the series.
As originally shopped around, the pilot included an unaltered (and unlicensed) version of Ronnie James Dio's Rainbow in the Dark as the theme song. Once the show was actually picked up the producers consulted with Dio and ultimately brought him onboard. The writer/director's vision of the theme song had it being played on violin and piano with only a few vocals as the song faded out. Dio proved to be a perfectionist about this rewrite, repeatedly throwing out the works of a half dozen violinists before finally teaching himself the violin in four weeks of frenzied instruction in order to do it right. Ultimately Dio played both the violin and piano parts of the theme song as well as dozens of variants for various use in the soundtrack of the show. He did not record new vocals though, as he claimed the vocals he recorded when he was younger were of better quality than anything he could do today. Dio also played dozens (some say hundreds) of uncredited roles in the first season. This was the norm for everyone involved with the show as basic production costs along with Tennant's and Dio's salary ate up almost the entire budget. Some claim that his soundtrack work with RtMH reinvigorated his career and directly led to the late career renaissance that he had from 2001 until his death in 2010.