Since The Cat Creeps (1930) is a lost film, the footage used in "Boo" is the only material from it known to exist.
Even though this short was produced by Universal Studios, the makers decided not to use footage from the company's own version of Dracula (1931), opting instead to use footage from the German Nosferatu (1922) film of 10 years earlier.
This is the first film to feature both Dracula and Frankenstein's Monster, although only via archive footage from separate movies. True movies made with both characters would not come about until the 1940s.
Boo was re-released by Universal in 2004 on DVD as part of the extras of Frankenstein (1931). It has since appeared on later home video releases of Frankenstein.
The unnamed narrator pronounces the suffix of Frankenstein as "steen", even though "stine" had been established in Frankenstein (1931) (whence the footage originates) and would be retained in all future Universal monster installments.