Alison Irwin was a houseguest in Big Brother 4 and later appeared in Big Brother All Stars. She was known for flirting with and manipulating several of the male houseguests, and being member of the Elite Eight alliance. When the Elite Eight crumbled, she formed an all-girls alliance fellow houseguests Jun Song and Erika Landin known as Girl Power. Alison won the final HoH and decided to take Jun with her to final 2. The jurors were extremely disappointed with the final 2 and decided to vote for Jun over Alison, deeming her as the 'lesser of two evils', thus making Alison the runner-up. Her ex-boyfriend Justin Giovinco was also in the house, as part of the X-Factor twist. During this season, she became the first houseguest in Big Brother history to never be nominated on eviction night. In fact, all three times the Power of Veto was used, it was to take Allison off the block.
In Big Brother All Stars, she was among the 14 out of 20 contestants chosen to go back into the house. In the first week, Alison, along with Danielle became part of a plan to make sure Jase disagreed with Janelle's nominations in order to make sure the two HoHs were automatically nominated together. This later backfired when Jase told Janelle about their plan, leading to both Alison and Danielle being nominated for eviction. When she did not win the PoV, Mike and Will campaigned for Alison, feeling that she would be a better ally to go after the Sovereign Six as opposed to Danielle. However, she was evicted by a 8 to 2, becoming the first houseguest evicted.
Alison became the first HouseGuest to make it to the finale and never be a nominee on eviction night.
Alison became the first female HouseGuest to win the Power of Veto twice.
Alison became the first female houseguest to win the Power of Veto twice in a row.
She is the only female to win HoH multiple times in Big Brother 4
She is also the only female to win the PoV twice in Big Brother 4.
In her original season, the three times the Power of Veto was used were on Alison.
Alison is the first HouseGuest to win the POV before nominations were made. This would happen again in Big Brother 14, when Ian won a POV before Frank made his nominations, as a consequence of Frank opening Pandora's Box.