Julie London – “Mickey Mouse March” (it’s a YSI, sorry readers from the future).
This song is tucked away at the end of London’s Nice Girls Don’t Stay For Breakfast album, and is indeed a sultry version of the M-I-C-K-E-Y Mouse theme. It’s odd, and not necessarily good, but it seems quite an early example of i) a ‘classy’ performer reaching out for a ‘trash’ artefact and ii) a style or genre being self-conscious of itself as a style, and hence able to apply that style to ‘unlikely’ material.
(This is 1967 though, which is later than I originally thought, so quite possibly the novelty cover version was already popular as a move.)