Rylan Clark and Frankie Dettori were told during the launch show to send either themselves or the former Hills stars to live in the "basement pigsty".
After Rylan and Frankie had chosen the Americans to be the basement dwellers, Big Brother later that night allowed housemates from upstairs and downstairs into the garden together, although the latter group were enclosed behind a mesh fence.
While the other housemates got acquainted, Pratt and Montag refused to enter the garden, with Heidi saying it would be painful to see how lovely the outside was while they were stuck in their enclosure.
When Frankie asked about the pair's absence, Sam Robertson went down to fetch them, only for Spencer to say: "I'm done with them [the upstairs housemates], they're on the cut list."
Speaking to Big Brother later on, Spencer joked: "We're having a blast. Our basement is the best, everyone is down to earth."
He then went on: "The decision by singer boy and jockey man was not a good decision; they should have sacrificed themselves as team players. I wouldn't have put myself above others, it's inconsiderate, selfish."
Rylan later described Spencer and Heidi's decision not to come into the garden as "odd".
"They've done enough reality shows," he told Big Brother. "If they've got the hump, f**k 'em, I can't stand fake people. If you've got a problem say it, it could be a bit of drams."
Photo gallery - Celebrity Big Brother day 1: