: Howard is forced to eat a granola bar containing peanuts to trigger a mild allergic reaction, ensuring Leonard stays at the hospital long enough for Penny to finish party preparations.

: To keep Leonard occupied, Penny tasks Sheldon with taking him to an electronics store. This backfires when Sheldon becomes hyper-fixated on choosing a new router, effectively "trapping" Leonard in the store.

: Howard’s willingness to undergo an allergic reaction—though played for laughs—highlights the lengths to which the group will go to please Penny and support Leonard.

The episode follows Penny’s attempt to throw Leonard his first-ever birthday party after discovering he has never had one. The plot splits into two main threads: Leonard and Sheldon’s "distraction" trip to an electronics store, and Howard’s increasingly desperate (and dangerous) attempts to keep Leonard away from the apartment while Penny prepares. Key Plot Points

Analysis of The Big Bang Theory : "The Peanut Reaction" (S1E16)