Continuity mistake: After Brian finds the note Alf left, we see William put the note under the microscope to inspect the tear drops. When William says "I'm going to go find him," he stands up and we see him leave the note on the microscope. When the camera cuts to William walking through the door, he all of a sudden has the note in his hand that was left on the microscope. (00:12:55 - 00:13:35)
Continuity mistake: When ALF writes the letter he uses a pencil, but when the camera shows the letter it is written in red ink.
Continuity mistake: When Kate says "I don't believe this" she is holding a cup. The shot changes, she isn't.
Continuity mistake: During the opening scene Lucky keeps changing position.
Answer: Mr Tanner actually asks Alf, "Why are you carrying our towels through the den?" The streaming subtitles are wrong when it substitutes "damp" for "den" twice. It's possible the error originated from the VHS or DVD, which occurs often.
Super Grover ★
Yes, I was re-watching episodes, and I heard "den" the next time. Thank you for answering, though.