Continuity mistake: When the bullies put the snake in Courtney's bag, it's brown. When Finley takes it out, it's changed to black, and is also a rubber snake. And when Courtney picks it up, it's real again, and is now yellow.
Revealing mistake: If you look closely, you can see human eyes inside of the mud monster's left eye. Pausing or slowing down is not required or necessary, but is easier to see if you do.
Answer: He repeatedly warns him against using the universal remote for bad purposes. However, Seth, blinded by remote's abilities, completely ignores and disregards Tony's warnings and uses the remote when and how he pleases, which eventually turns against him.