The Launch Acceleration

The gas Leonard brings to Penny is Sulfur Hexafluoride. It is 6 times denser than air, thus causing the 'Darth Vader' voice. It is an inert gas and safe to breathe in small quantities.

At the rental suit shop Sheldon explains that he is wearing long underwear in order to avoid coming in touch with someone else's sweat when trying the suit. Raj then says that his reaction is not as entertaining as when he rents bowling shoes. But in The Wheaton Recurrence (2010) we learn that Sheldon actually has his own bowling shoes which he disinfects before wearing them anyway.

CHUCK LORRE PRODUCTIONS, #387 He appeared normal. He spoke and behaved just like anyone else. The fact that he had no heart was very well concealed. Well, that's not entirely true. He did have one. It was just not in his possession at the moment. And this is where the story gets complicated. The woman who had the darn thing was blithely unaware of the fact. Well, that's not entirely true either. She knew that she'd left the relationship with more stuff than when she entered it, she just hadn't bothered to do a proper inventory. (Had she done so, she would have found several other hearts, as well as a few sets of balls.) Regardless, his dilemma remained the same. A woman had absconded with a vital organ and the gnawing emptiness he felt was a direct reflection of that vacancy. Well, that's not entirely true either. The gnawing thing had actually been with him since he was a child. He just liked to assign blame for the condition.

References The Bullwinkle Show (1959)