It was stingray, not thunderbirds he watched in the hotel rm...
"I'm not living with you, we just occupy the same cage, that's all!"
There are always mistakes in movies done in films sometimes.
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You're right. ITC Entertainment, the British company that owns the old Gerry Anderson shows e.g. Stingray also made the Stepfather movies (and The Muppet Show FYI).
I'm not sure about the final cut of the movie, but I just watched the outtake reel on the Synapse DVD and because they could only use the Stingray visuals and not the sound, they had a cast ADR the footage (including Bruce Campbell) and the soundtrack mentions "Thunderbird 1, Thunderbird 2" etc...I guess they figured it would be more easily recognisable with the most popular show of that stable.