In Wii Fit
In Wii Fit, pets don't make a major appearance, cats not appearing at all, and dogs only appearing in Basic Run.
In Wii Fit Plus and Wii Fit U
'Pet Miis are featured in Wii Fit Plus and Wii Fit U. beke Baby miis, They are used to measure weight. However, unlike regular Miis (and once Frisbe like Baby miis) you cannot play training with them. However, unlike Baby miis the training activities are won/unlocked; considering they do not grow up into Frisbee miis due to the fact they are pets and therefore a different species (babies are the same species and are much rather just young and as a result, they are much less multitasked.) In Wii Fit U, Dog Miis (Not Cats) can use a Fit Meter.