There was a gaggle of geese in the field.
There were geese in the field.
There was a mob of fans on the bleachers.
There were many fans on the bleachers.
There was a throuple fucking on the bed.
There were three people fucking on the bed.
Gaggle, mob and throuple are singular terms and should be treated as such. The same goes with pair.
Note that there's a difference between UK and US English - UK often uses singular nouns that refer to groups of people (eg government, committee, team) as if they were plural, when referring to the members rather than the entity as a whole.
The Government announced that it has a new policy.
The Government are a bunch of muppets.