When Mac and Jack enter Mama's Diner, we see a picture of an English bulldog named "Frog". That was the dog featured in a few episodes of the original series that befriended the original Mac.
In the original series, Jessie Colton (played by Richard Lawson) has the goal of making enough money bounty hunting to retire to Hawaii. The "Hawaii" bumper sticker is a nod to that.
The pizza box in the fire pit scene at Mac's house says "Zlotoff's Pizzeria". Lee David Zlotoff is the creator of the Original Show.
The bumper sticker "I wish I was in Hawaii" is a nod to there future crossover episode with Hawaii Five-O.
For unknown reasons, this episode was skipped over during the Season 1 TV premiere in Germany in Summer 2017. German TV channel Sat. 1 aired it half a year later (in March 2018).