Anda y venga

Question

Can anda and venga be used the same way? Come on!I have also heard " anda anda!" Is that just for emphasis?

Answer

Hola Mark
Yes, anda and venga are interchangeable and both meaning "come on".
Also, the word anda is very versatile in Spanish, you can use it double as you said, "anda, anda" and this goes with the tone that you use or facial expression, so you may be reacting to something that you don't believe:

- Hoy he visto a Brad Pitt en la calle.
- Anda, anda, no digas tonterias.
 
-I've seen Brad Pitt in the street.
-Come on, don't be silly.

Or for example, to express some kind of reproach towards someone:

- ¡Oh no! Me he echado todo el chocolate caliente encima.
- Anda, anda, pero qué desastre eres. 
 
- Oh, no! I spilled the whole hot chocolate all over me.
- Oh my god! You're so clumsy. [lit: you're a disaster]

The repetition of the word is for emphasis.
Saludos

Answer

I always remember the use of 'anda' from the catchcry of famous cartoon character, Speedy Gonzales. As the lightning fast Mexican mouse would speed to the cheese past the unfortunate 'El Gringo Pussygato Stupido', Sylvester, he would call to his companions "Arriba Arriba Andale Andale"