- The Cast Showoff: Ellen McLain is an operatic singer, which means she sings one hell of a credits song.
- Creator Backlash: Portal's writer, Erik Wolpaw, grew sick of the non-stop cake jokes after the first game. In this interview, he claimed there wouldn't be any references to it in the sequel — only to include things like one of Doug Rattmann's drawings depicting the cake (at 1:07 in the video), and the binary code in Part 1 of the comic translating to "the cake is a lie." In the end, Wolpaw just couldn't resist.
- DVD Commentary: Both games have a "Developer Commentary" option. Here, there are speech bubbles scattered around the maps, and pressing the use key on them gives a fun fact about development.
- Defictionalization: The Portal Gun
- Prop Recycling:
- The "High-Energy Pellet" is the same sprite and sound effects as the Combine's energy orbs. Its effect on living beings is pretty much the same as well, although Gordon's suit seems to block its damage.
- Chell's leg-springs were part of an enemy cut from Half-Life 2, the Combine Assassin.
- The sentry turrets have largely the same behavior as Half-Life 2's Combine turrets. They also use the same sound effects in the trailer and during Portal 2's ending.
- Chell actually vocally reacts to impact damage from cubes and other such things. The sound bites used for this are from female NPCs who take damage in Half-Life 2. In Portal 2, though, this doesn't happen.
- Serendipity Writes the Plot: According to Portal 2 - The Final Hours, the reason the games take place in the Half-Life universe was to justify the recycled assets from Half-Life 2, which were a lot more pronounced in early development due to the game's small development team.
- Throw It In!: In this interview, Word of God reveals that the blood splatters weren't meant to be in the game at all. However, they weren't even noticed until too late in development, and were so ingrained into the engine that, by that point, it would have been better to just leave them in the game. Valve went out of their way to remove the blood splatters for the sequel, however, hence its lower rating compared to the original.
- Trope Namer:
- What Could Have Been:
- In earlier concepts for a sequel to Portal, Cave Johnson was positioned to play a significantly larger role, including being subject to Brain Uploading (which, in the final release, he wanted, but he likely died before it could happen), and undergoing an existential crisis concerning the fact.
- According to the Final Hours of Portal 2, Peer Review was going to contain a single player campaign as well. The original plan was for players to be either ATLAS or P-body, who would be recruited by Rick to stop a brain-uploaded Cave Johnson from taking over the Enrichment Center. Valve decided it would require too many resources for ''just'' a DLC...
Trivia / Portal