Porthos

In the TV series, Star Trek: Enterprise, Captain Archer owns a beagle whose name is based off of one of the Three Musketeers, that is, Porthos.

Appearance
He appears as any normal male Beagle, of probably 11 months of age.

Behavior
In another timeline, Porthos was an aggressive Rottweiler. Normally, Porthos is quiet and sweet, but will bark when strange things happen on the ship. Porthos is commonly seen laying on Archer's bed. Porthos likes cheese, but it sometimes causes gastrointestinal distress. Porthos was one of a litter with 4 puppies. His siblings are named Athos, D'Artagnan, and Aramis. Porthos was played by 3 different beagles. Their names were Prada, Breezy, and Windy.

Source
Memory Alpha