This inside joke is based on the popular Donkey Kong "Expand Dong" meme. While on a late night drive to Shari's for some food and pieshakes the use of expand dong banter was at an all-time high. It is at this time that Alpha told this joke
There was a guy who owned a store called Dong. He had a lot of customers and was running out of space to store all of his merchandise. So he had to make the building bigger and expand Dong.
Meme credit goes to the page Memery Glands on Facebook