We had yuge customer satisfaction with Star Trek
A portable CD player running on endless shuffle in the server rack, playing a collection of quotes from Star Trek into the on-hold input. Some callers even asked to be put back into the queue, so they could listen some more.
Probably was this one or a similar collection: https://www.musik-sammler.de/media/604872/
The CD player was later replaced by a bunch of MP3 files on an Asterisk appliance and kept trekking until late last year.