In the opening scene when we see Jack and Victor as small boys and then turning into old men, look at Victor when he is a small boy. At one point he looks at the crew. It is over in a split second. Blink and you will miss it.
In series 5 in the episode "Fresh Lick," when Tam shows Navid the video tape in the back of the shop, the customer gets impatient and says she is going to Kohli's. This is a mention to Navid's actor Sanjeev Kohli.