Freddy Fog jumped into his pond. (The antecedent of the pronoun his is Freddy.)
When Tom Turtle saw what a nice pond it was, he decided to toddle over. (The antecedent of it is pond.)
Freddy Frog and Tom Turtle jumped into their pond. (The antecedent of the pronoun there is Freddy Frog and Tom Turtle.)
The social perception we reach in this ponderous tale is either that Tom Turtle has been working out at the gym and has bigger biceps than Freddy Frog and can jump into any pool he wishes or that Freddy Frog is a self-sacrificing little snit who hopes to ingratiate himself with the pond populace. Whatever.
Indefinite pronouns refer to nonspecific persons or things. They should be treated as singular in formal English and would, therefore, take singular verbs. Here are some examples of indefinite pronouns:
anybody either neither somebody
anyone everybody nobody someone
anything everyone none something
each everything no one
In class everyone performs at his or her fitness level. (The indefinite pronoun everyone takes a singular verb performs and a singular pronoun his/her.)
Treat collective nouns as singular unless the meaning is clearly plural. Collective nouns such as jury, committee, audience, crowd, class, troop, family, team, and couple name a class or a group. Usually the group functions as a unit, so the pronoun should be singular.
The committee granted its permission to build. (The committee is thought of as acting as a unit.
The committee put their signatures on the document. (The committee is thought of as acting as individuals.
Treat most compound antecedents connected by and as plural.
Joanne and John moved to the mountains where they built a log cabin. The antecedent of they is Joanne and John.