The Pet Shop is a location in Springfield that sells animals. When Bart Simpson plays a prank where he exclaims "Testing!" loudly into several megaphones, the glass at this shop breaks and the parrots sold here all repeat "Testing!" several times.
Aside from this, it also sold hamsters, with some goons (presumably some of Smithers' henchmen) also exiting the shop to assault the Simpson family while they were pursuing Smithers due to his abducting Maggie as a result of a stolen diamond being lodged into her mouth.
