A Royal Air Force parade was recently cancelled in Lincolnshire, England when a possible bomb was found in a telephone booth. The bomb turned out to be an air freshener. From BBC News:
A BT spokesman said air fresheners had been installed in enclosed phone boxes for years without problems…
The BT spokesman said: "We do put air fresheners in some phone boxes – we like to make the environment as pleasant as possible for people using a payphone to make a call.
"Some people have been known to use phone boxes for reasons other than wanting to phone someone.