"Here is something that is rare to see in an Aldi store," one woman wrote on Facebook.

"It is the first time I have ever seen an assistance cat anywhere in public."

Although some users thought the assistance cat in the trolley was adorable, many were not happy with the feline being inside the store.

"So anyone can buy a harness for an animal and call it an assistance pet and take it anywhere. Ridiculous," one person wrote.

"Animals should not be in trolleys. Cats especially walk-in cat litter!" another added.

However, many stood up for the customer and their cat by saying that the trolleys are usually filthy and it would be more dangerous to have the cat walking on a leash.

"I don't know why everyone is complaining about the cat in the seat. I never use this part of the trolley, it is designed to put young children. Some who still wear nappies or a being toilet trained," one person wrote.

"You could recommend that he sits on a blanket like I used to bring for my daughter... I carry wipes and bags with me and always wash veggies," another said.

Another person highlighted the possible risk of allergic reactions if a child were to sit in the trolley after the cat had used it.

"I'm not against assistance animals at all but from a mum with a child with a severe allergy to cats and dogs I don't think it should be in the trolley," one mum wrote.

Think Mental Health Clinical Director, Vanessa Hamilton, told Yahoo News Australia that we should be prepared to see more cats as assistance animals, after seeing an increase in people registering their felines.

"Animal-assisted intervention (AAI) is a growth area that is showing promise as a complementary treatment for individuals who have experienced trauma," Hamilton said.

"The most prevalent outcome of AAI is a reduction in symptoms of depression, anxiety and post-traumatic stress.

"There is strong anecdotal evidence to support animals as a unique additional element to address several symptoms of psychological distress."