Robin desperately tries to get back together with Barney. Ted subs as Marvin's nanny, but Marshall and Lily realize that he's becoming way too close with their son.
This episode provides examples of:
- Best Served Cold: Lily and Marshall wait three years to take Ted's daughter to see Santa without him in revenge for his "firsts" with Marvin.
- Bullet Proof Human Shield: Played with. Barney uses Robin as a human shield in laser tag.
- Double-Meaning Title: "Lobster Crawl" comes from Robin's obsession with lobster and how she comes back crawling to it despite the fact that it can kill her. On the subplot of the episode, Lily and Marshall are upset because they missed Marvin's first crawl (and other firsts because Ted kept hogging Marvin to himself).
- Forbidden Fruit: Robin becomes obsessed with Barney once again only after Barney said to her face that he already gave up on her. Lily calls her out on this, since it also happened when the doctor told her that she was allergic to lobster, which caused her to eat it to the point of almost dying from the allergic reaction.
- Girl on Girl Is Hot: Lily's suggestion for Robin to win Barney's attention. It backfires on Lily when Robin gets her friend Brandi to be the other girl. It backfires on Robin when Barney leaves with Brandi.
- Unrequited Love Switcheroo: Now that Barney is no longer interested in Robin, she's become obsessed with him.
