US jokes!
Scene S3E18
Rachel: it's a hypnosis tape.
Ross: Pffhah.
Ra: (to Ross) What's your problem?
Ro: it's just that hypnosis is beyond crap.
Ra: Ross, I watched you get hypnotised in Atlantic City.
Ro: Hey, that guy did not hypnotise me!.
Ra: Oh right, 【'cause you always pull your pants down at the count of three and play Wipe-out on your butt cheeks.】
...
S3E19
Ross: Hey, how'd the date go with Mr. Millionaire?
Chandler: Mr. Millionaire, 【new from Snooty Playthings! Third wife sold separately.】
Monica: he has everything. Plus! He actually has everything.
Chandler: 【Life-sized Imperial Storm Troopers from Sharper Image?】
Monica: Two.
Chandler: Wow!! 【Can Joey and I put them on and fight?】
.....
s3e19
Joey: (entering, dancing and singing) Oh mommie, oh daddie, I am a big old baddie! (He dances around the dinner table and exits)
Ross: I guess he musta gotten the part in that play.
Chandler: Yeah, either that, or 【Gloria Estefan was right, eventually, the rhythm is going to get you.】

Question

US jokes!
Scene S3E18
Rachel:  it's a hypnosis tape.
Ross: Pffhah.
Ra: (to Ross) What's your problem?
Ro:  it's just that hypnosis is beyond crap.
Ra: Ross, I watched you get hypnotised in Atlantic City.
Ro: Hey, that guy did not hypnotise me!.
Ra: Oh right, 【'cause you always pull your pants down at the count of three and play Wipe-out on your butt cheeks.】
...
 S3E19
Ross: Hey, how'd the date go with Mr. Millionaire?
Chandler: Mr. Millionaire, 【new from Snooty Playthings! Third wife sold separately.】
Monica:  he has everything. Plus! He actually has everything.
Chandler: 【Life-sized Imperial Storm Troopers from Sharper Image?】
Monica: Two.
Chandler: Wow!! 【Can Joey and I put them on and fight?】
.....
s3e19
Joey: (entering, dancing and singing) Oh mommie, oh daddie, I am a big old baddie! (He dances around the dinner table and exits) 
Ross: I guess he musta gotten the part in that play.
Chandler: Yeah, either that, or 【Gloria Estefan was right, eventually, the rhythm is going to get you.】

Answer

"Snooty Playthings" was, I would imagine, a company made-up by Chandler that sells ridiculously priced things to people who are rich, or want to be.  "Mr. Millionaire" would then be a really ritzy toy purchased from Snooty Playthings. To complete the set, one could purchase "Third Wife" from "Snooty Playthings" as well.

In other words ,when Ross said "Mr. Millionaire", it probably made Chandler think of a commercial he had seen and he turned "Mr. Millionaire" into a toy that could be bought from a store and he was making his own little commercial about it. Or something along those lines.

Answer

Q1: "Wipe Out" was a popular song in the 1960s. The title refers to being knocked off one's surfboard. How Ross might have played this song on the cheeks of his butt is a prospect I cannot begin to fathom.
Q2: "Snooty Playthings" is a generic, joking reference to nothing real, I believe. Some millionaires marry more than once. "Sold separately" is a phrase used in commercials mentioning additional things like batteries. Sharper Image is a retail outlet selling unique items. Storm Troopers in the Star Wars movies were soldiers wearing special body armor.
Q3. Yes, Gloria Estefan wrote and performed a song titled "The rhythm is gonna get you". The phrase "get you" means to deeply affect a person.

Answer

Q1: what’s is wipe-out? Is it a game? How did ross play it with his butt cheeks?
Q2：i love chandler, he teaches me so much about American culture, though i have to dig a little deeper to understand them, haha. Could you please help explain the stuff in the bracket?
Q3: it’s chandler’s joke again!! I googled Gloria Estefan and understand she is a singer, but did she actually sing “the rhythm is going to get you” and what does “get you” mean?

thank you so much for your help:) have a nice weekend~