So what's the recipe for success?
Smart, hot tour guides: Whether you take the day or night tour, you won't be bogged down with dense, droning stories. Fat Tire's guides are easy on the eyes, quick-witted and filled with clever tidbits, like where to find the two secret Louvre entrances (down the staircases under the statues). They've also got the cool history you actually want to hear about, like the guy who plummeted to his death from the Eiffel Tower after his experimental "bat suit" malfunctioned in 1912.
Cali-style beach cruisers: The bikes rock. Cushy wide seats--a must on Paris' bumpy streets--make for a breezy ride that even your mom could handle.
Free wine: The day tour is sweet but the wine is free-flowing on the night tour, which also includes a ninety minute boat cruise up the Seine. The Fat Tire guys like to party, so don't be surprised if you continue the drink-fest at some local bar.
And here's one extra tip: The Fat Tire headquarters near the Eiffel Tower is the ideal place to get online on the cheap (with English keyboards!) and socialize with other travelers. Even European travel guru Rick Steves was checking email there recently, fresh off his trip to Iran.