Extending functions from integers to reals in a "nice" way.
Yes. We can even make $g$ equal to its Taylor series around every point, everywhere -- or, in other word, every function $\mathbb Z\to\mathbb C$ can be extended to an analytic function $\mathbb C\to\mathbb C$.
We can construct $g$ as the sum of a sequence of polynomials $g_1, g_2, g_3, \ldots$, such that
- $g_n$ is zero on $[-(n-1),n-1]\cap\mathbb Z$
- $g_n$ has the right values at $-n$ and $n$ to give the sum the right value at these two points.
- $|g_n(z)|<2^{-n}$ for $|z|\le n-1$.
The last of these properties will guarantee that the sum exists everywhere and is analytic everywhere (since it converges uniformly on every bounded subset of $\mathbb C$).
No matter what the values of $g_n(-n)$ and $g_n(n)$ need to be we can always achieve all the required properties by choosing $$ g_n(z) = (b+cz)z^m\prod_{k=-(n-1)}^{n-1} (z-k) $$ for appropriate constants $m$, $b$ and $c$. (Choosing $m$ large enough can make the magnitude of the value of the function on the disk $B_{n-1}(0)$ small enough compared with the values at $-n$ and $n$ that the third property can be achieved).
Of course, this extension is not unique -- at the very least we can add any multiple of $\sin(\pi z)$ we want to the result without losing analyticity.
Or, if we only want $g$ to be analytic on $\mathbb R$, we can simply choose $$ g(x) = \sum_{k\in\mathbb Z} \operatorname{sinc}(x-k)^{m_k} f(k) $$ where $\operatorname{sinc}(x)=\frac{\sin(\pi x)}{\pi x}$ and $m_k$ is chosen large enough that $\operatorname{sinc}(x)^{m_k}f(k) < 2^{-|k|}$ for all $|x|>1$.