If you need the answer to the joke it is "a watchman"
A person who collects beetles is a coleopterist.
Bibliophile
supernatural
collecter
A cravatologist.
a strawber.
Holrologist might be a good fit. Horology is the science of time, time keepers -- clocks, watches, etc., and timekeeping.
A car collector?
a button collector
A paper collector
A badge collector.
A gem collector