Others who ran the store
Among the Muppets who ran the store:
Oscar, who Mr. Hooper convinced to mind the store with the allure of four large trash cans inside the store. But when Hooper returned, Oscar had taken most of the garbage out of the cans and "decorated" the store with it. For example, large sheets of dirty brown paper served as the "curtains". Needless to say, Hooper was quite angry with Oscar, and made Oscar take all the trash back with him to his place (some punishment that was, Oscar was only too happy to do it).
On another occasion, Oscar was manning the window by the newsstand where a group of 5 kids were intending to get ice cream. A number 5 was superimposed over an upper corner of the screen, the number of ice cream cones Oscar had to remember to prepare. Then Gordon (Robinson) came and pulled one of the girls away, changing the number to 4. Kids kept coming and going, and the number onscreen kept changing. When the number was once again 5, Oscar bellowed, "There's the 5 (onscreen), back again. Sigh... why don't you make up your mind."
A few seasons later, Cookie Monster minded the store. This was where Mr. Hooper made him promise not to eat from a large glass cookie jar on a shelf. Of course when Hooper returned, CM had consumed all other edibles in the store, as well as everything non-food that wasn't nailed down! He then helped himself to the cookies "for dessert". They gave CM a hammer to help rebuild the store -- CM attempted to eat the hammer before the adults stopped him.
Another time, Luis was nitpicking at Tom's doings in the store, and Tom was somehow complaining about Luis' Fix-it Shop work. The old "if you think you can do better, YOU do it" ensued, so Luis and Tom switched jobs for the day. I'm not sure how Luis made a mess of things while working Hooper's store, though I vaguely seem to recall he burned the toast. As for Tom in the Fix-it Shop, Big Bird came in with an antique wall clock that wasn't chiming. Tom reached his hand behind the clock's works, said "ah, I feel it (what's malfunctioning)", and summarily repaired the chiming mechanism -- or did he? To test it out, me moved the hands to 12:00, and Big Bird counted 12 chimes. Only problem is, it did not stop at 12, it just kept going. BB sadly said something like "Is it 13:00, 14:00 or even, 200 o'clock? You've ruined my clock!" Luis and Tom decided that it was best to stick to one's own trade.