Fan Nickname: "Baxtabber" for Baxter, and "Staypuff" for Alex (but that one's used in the comic as well). The nicknames from the actual show are often used as well.
It's also become something of a trend to call popular female players "goddesses", like with Montana and Ker.
"HUMAN COCKROACH" was a semi-popular one for Bonnie.
The alliance of Casey, Claus, and Juiced Up was commonly referred to as "The Three Stooges".
Schedule Slip: Apparently had one in the beginning of the first season when the author had to switch from modified sprites to 100% custom ones. After that, however, it is completely averted; this has lead to some people lauding him for being the god of buffer. However, the author has recently notified that Season 10 will be delayed a bit, most likely putting an end to the aversion. The season premiere was posted on the first of July, and it seems to be going on smoothly again.
Season 12 has also been confirmed to be delayed.
Same goes for Season 13, though not quite as long.
What Could Have Been: SWSU has detailed a number of scenarios he considered for the various seasons after they had ended:
Brains vs. Brawn: He had originally planned to have a Corrupt the Cutie arc for Bitsy, involving Mary's evilness, but scrapped the idea after he couldn't make Bitsy's "evil" face look convincing and ended up using it for Hope in the next season instead.
Season 3: SWSU said he wanted to make it a story of how someone lost it instead of how someone won, it referring to Baxter losing and Montana winning. He had originally considered Beth as a winner, but she was as boring as hell and would have been a lot less satisfying a winner. Additionally, the season was supposed to be nicknamed "The Gender Wars", but it was scrapped after the name was decided to be too cheesy.
Fans vs Canons 1: SWSU had plenty of canon choices when he selected the fan characters he needed for the season... those included...
The Tough Villain that leaves on Episode 1 (which ended up being Sephiroth): Wesker from Resident Evil, Shadow the Hedgehog from Sonic, Owen from Total Drama (the latter probably wouldn't have been a villain)
The Quiet Early Boot Girl (which ended up being Shiki): Kairi from Kingdom Hearts, and Cream the Rabbit from Sonic.
The Med Evac (which ended up being Trent): Cody from Total Drama
The Useless Girl (which ended up bing Bulma): Rouge the Bat from Sonic, Lindsay from Total Drama
The Alpha (which ended up being Riku): Cloud from Final Fantasy VII, Duncan from Total Drama, Sonic the Hedgehog
The Villain (which ended up being Minerva): Heather from Total Drama.
Over The Top Guy (which ended up being P. Bear): Sonic the Hedgehog
The only people that were locks were Rebecca and Lilly.
Cursed Islands: Instead of Marius winning, he had considered Amy, who would have been a more safe, 'heroic' pick, as well as Maria/Mo which would have been hilarious considering how demented she was; to be fair, though, he only considered Maria as a winner when he didn't know about Mo. Also, he had initially planned for the final vote to go 4-3-0 with Gatemaster receiving no votes, but changed it to a 3-2-2 split when he realized that there was no plausible way to give Marius a fourth vote.
Season 6, All-Stars, was originally planned to be a Pre-Merge vs. Post-Merge season, but was changed when SWSU realized he was leaving out too many big characters. Prospects for the pre-merge tribe included Eugene, Cassie, Phil from Season 1, Mihoshi, Drake and Audrey.
Season 7: Ker, the winner of the season, was fighting in a three-way battle between Betty and Bo. Betty was ousted because she would be yet another competent winner, and Bo was ousted because SWSU felt that Ker had more colorful moments to offer.
Season 8: SWSU initially had Emilee as the winner, but changed it to Melanie because he wanted a more negative winner.
Season 10: Wrecker was originally planned to be a contestant, but his owner declined SWSU's offer for him to come back, which caused Quadratic to return instead and the booting order to be changed (Chloe would have been the second one out with Wrecker in). Jessica was originally considered being brought back instead of Miranda as well.
Originally, the Retro Tribe didn't exist in Season 10. Instead, the tribe was made up of some people from the other tribes not represented in Seasons 7, 8 and 9. Prospects for this "Misfit" tribe included Betty, Skazzatrazz, Iraenus, Brenton and Jocasta.
Season 11: Originally, Artemis was going to win and Crisco would have backstabbed his way to the finals, but SWSU decided that would be too clichéd.
Fans vs Canons 2: SWSU considered having Kim be dominant throughout the entire game, but decided it would make her too unlikeable and let Enter control the earlier boots instead.
Season 13: Orwell's placement was said to have changed repeatedly during development, and SWSU says his current spot is for the better.
Word of Gay: Norman was confirmed to be gay long before he said so himself. Also Lyle from Season 1.