Brain's Disguises: auction bidder and waiter
Even though the coin cases were locked up, Penny and the little snakes were still able to get into the cases with no problems.
When Brain had pulled the MAD agent's extremely stretchy snake tie around the corner with a book and up the stairs, it was tight against the wall. When Gadget came around the corner it was still tight against the wall but when Brain threw the book the stretched out tie was now in-between Gadget's legs.
Gadget: Wowzers, I haven't seen this much snow since that episode in the arctic.
Gadget is breaking the fourth wall and referencing to the episode Gone Went the Wind which was set in the North Pole region.
Gadget: (after capturing Prof. Venom with the help of the coin guard) Well, this time I had a little help Chief.
Chief Quimby: Just like you Gadget, always giving credit to someone else.
Gadget: I'm just terribly modest Chief. When you're the world's greatest detective you have to be.