The security code put on the Ferrari by Higgins is a throwback to the first episode of the original series where the exact same thing happens.
In Hawaii Five-0 (2010) season 7 episode 3, which is set in the same universe as this show, Kono Kalakaua reconnects with an old surfing buddy who has lost both legs while serving in the military. They go surfing together, which is very similar to to Rick and TC taking Shammy surfing in this episode.